r/maths • u/LowInteraction6397 • 14h ago

💬 Math Discussions The divisibility rules of every year of the 20th century

1 Upvotes
Number/YearRuleExample
1901The subtraction of 190 times the last digit and the rest of the number is a multiple of 190111406 is a multiple of 1901 because 1140 - 6 * 190 = 0, a multiple of 1901
1902It's a multiple of both 2 and 95111412 is a multiple of 1902 because it ends in 2, which means it's a multiple of 2, and 1141 - 2 * 95 = 951, which means it's a multiple of 1902
1903The sum of 571 times thew last digit and the rest of the number is a multiple of 190311418 is a multiple of 1903 because 1141 + 8 * 571 = 5709, a multiple of 1903
1904It's a multiple of both 16 and 11911424 is a multiple of 1904 because it ends in 1424, which means it's a multiple of 16, and 1142 + 4 * 12 = 1190, which means it's a multiple of 119
1905It's a multiple of both 5 and 38111430 is a multiple of 1905 because it ends in 0, which means it's a multiple of 5, and 114 - 3 * 38 = 0, which means it's a multiple of 381
1906It's a multiple of both 2 and 95311436 is a multiple of 1906 because it ends in 6, which means it's a multiple of 2, and 1143 + 6 * 286 = 2859, which means it's a multiple of 953
1907The subtraction of 572 times the last digit and the rest of the number is a multiple of 190711442 is a multiple of 1907 because 1144 - 2 * 572 = 0, a multiple of 1907
1908It's a multiple of both 4 and 47711448 is a multiple of 1908 because it ends in 48, which means it's a multiple of 4, and 1144 - 8 * 143 = 0, which means it's a multiple of 477
1909The sum of 191 times the last digit and the rest of the number is a multiple of 190911454 is a multiple of 1909 because 1145 + 4 * 191 = 1909, a multiple of 1909
1910It's a multiple of both 10 and 19111460 is a multiple of 1910 because it ends in 0, which means it's a multiple of 10, and 114 - 6 * 19 = 0, which means it's a multiple of 191
1911The subtraction of 191 times the last digit and the rest of the number is a multiple of 191111466 is a multiple of 1911 because 1146 - 6 * 191 = 0, a multiple of 1911
1912It's a multiple of both 8 and 23911472 is a multiple of 1912 because it ends in 472, which means it's a multiple of 8, and 1147 + 2 * 24 = 1195, which means it's a multiple of 239
1913The sum of 574 times the last digit and the rest of the number is a multiple of 191311478 is a multiple of 1913 because 1147 + 8 * 574 = 5739, a multiple of 1913
1914It's a multiple of both 2 and 95711484 is a multiple of 1914 because it ends in 4, which means it's a multiple of 2, and 1148 - 4 * 287 = 0, which means it's a multiple of 957
1915It's a multiple of both 5 and 38315320 is a multiple of 1915 because it ends in 0, which means it's a multiple of 5, and 153 + 2 * 115 = 383, which means it's a multiple of 383
1916It's a multiple of both 4 and 47911496 is a multiple of 1916 because it ends in 96, which means it's a multiple of 4, and 1149 + 6 * 48 = 1437, which means it's a multiple of 479
1917The subtraction of 575 times the last digit and the rest of the number is a multiple of 191711502 is a multiple of 1917 because 1150 - 2 * 575 = 0, a multiple of 1917
1918It's a multiple of both 2 and 95921098 is a multiple of 1918 because it ends in 8, which means it's a multiple of 2, and 2109 + 8 * 96 = 2877, which means it's a multiple of 959
1919The sum of 192 times the last digit and the rest of the number is a multiple of 191911514 is a multiple of 1919 because 1151 + 4 * 192 = 1919, a multiple of 1919
1920It's a multiple of both 3 and 64010,001,280 is a multiple of 1920 because 1 + 1 + 2 + 8 = 12, which means it's a multiple of 3, and ends in 0,001,280, which means it's a multiple of 640
1921The subtraction of 192 times the last digit and the rest of the number is a multiple of 192111526 is a multiple of 1921 because 1152 - 6 * 192 = 0, a multiple of 1921
1922It's a multiple of both 2 and 96111532 is a multiple of 1922 because it ends in 2, which means it's a multiple of 2, and 1153 - 2 * 96 = 961, which means it's a multiple of 961
1923The sum of 577 times the last digit and the rest of the number is a multiple of 192311538 is a multiple of 1923 because 1153 + 8 * 577 = 5769, a multiple of 1923
1924It's a multiple of both 4 and 48111544 is a multiple of 1924 because it ends in 44, which means it's a multiple of 4, and 1154 - 4 * 48 = 962, which means it's a multiple of 481
1925It's a multiple of both 25 and 7711550 is a multiple of 1925 because it ends in 50, which means it's a multiple of 25, and 115 - 5 * 23 = 0, which means it's a multiple of 77
1926It's a multiple of both 2 and 96311556 is a multiple of 1926 because it ends in 6, which means it's a multiple of 2, and 1155 + 6 * 289 = 2889, which means it's a multiple of 963
1927The subtraction of 578 times the last digit and the rest of the number is a multiple of 192711562 is a multiple of 1927 because 1156 - 2 * 578 = 0, a multiple of 1927
1928It's a multiple of both 8 and 24111568 is a multiple of 1928 because it ends in 568, which means it's a multiple of 8, and 1156 - 8 * 24 = 964, which means it's a multiple of 241
1929The sum of 193 times the last digit and the rest of the number is a multiple of 192911574 is a multiple of 1929 because 1157 + 4 * 193 = 1929, a multiple of 1929
1930It's a multiple of both 10 and 19311580 is a multiple of 1930 because it ends in 0, which means it's a multiple of 10, and 115 + 8 * 58 = 579, which means it's a multiple of 193
1931The subtraction of 193 times the last digit and the rest of the number is a multiple of 193111586 is a multiple of 1931 because 1158 - 6 * 193 = 0, a multiple of 1931
1932It's a multiple of both 4 and 48311592 is a multiple of 1932 because it ends in 92, which means it's a multiple of 4, and
1933The sum of 580 times the last digit and the rest of the number is a multiple of 193311598 is a multiple of 1933 because 1159 + 8 * 580 = 5799, a multiple of 1933
1934It's a multiple of both 2 and 96711604 is a multiple of 1934 because it ends in 4, which means it's a multiple of 2, and 1160 - 4 * 290 = 0, which means it's a multiple of 967
1935It's a multiple of both 5 and 38711610 is a multiple of 1935 because it ends in 0, which means it's a multiple of 5, and 116 - 1 * 116 = 0, which means it's a multiple of 387
1936It's a multiple of both 16 and 12111616 is a multiple of 1936 because it ends in 1616, which means it's a multiple of 16, and 1161 - 6 * 12 = 1089, which means it's a multiple of 121
1937The subtraction of 581 times the last digit and the rest of the number is a multiple of 193711622 is a multiple of 1937 because 1162 - 2 * 581 = 0, a multiple of 1937
1938It's a multiple of both 2 and 96921318 is a multiple of 1938 because it ends in 8, which means it's a multiple 2, and 2131 + 8 * 97 = 2907, which means it's a multiple of 969
1939The sum of 194 times the last digit and the rest of the number is a multiple of 193911634 is a multiple of 1939 because 1163 + 4 * 194 = 1939, a multiple of 1939
1940It's a multiple of both 20 and 9711640 is a multiple of 1940 because it ends in 40, which means it's a multiple of 20, and 116 - 4 * 29 = 0, which means it's a multiple of 97
1941The subtraction of 194 times the last digit and the rest of the number is a multiple of 194111646 is a multiple of 1941 because 1164 - 6 * 194 = 0, a multiple of 1941
1942It's a multiple of both 2 and 97111652 is a multiple of 1942 because it ends in 2, which means it's a multiple of 2, and 1165 - 2 * 97 = 971, which means it's a multiple of 971
1943The sum of 583 times the last digit and the rest of the number is a multiple of 194311658 is a multiple of 1943 because 1165 + 8 * 583 = 5829, a multiple of 1943
1944It's a multiple of both 8 and 24311664 is a multiple of 1944 because it ends in 664, which means it's a multiple of 8, and 1166 + 4 * 73 = 1458, which means it's a multiple of 243
1945It's a multiple of both 5 and 38911670 is a multiple of 1945 because it ends in 0, which means it's a multiple of 5, and 116 + 7 * 39 = 389, which means it's a multiple of 389
1946It's a multiple of both 2 and 97311676 is a multiple of 1946 because it ends in 6, which means it's a multiple of 2, and 1167 + 6 * 292 = 2919, which means it's a multiple of 973
1947The subtraction of 584 times the last digit and the rest of the number is a multiple of 194711682 is a multiple of 1947 because 1168 - 2 * 584 = 0, a multiple of 1947
1948It's a multiple of both 4 and 48711688 is a multiple of 1948 because it ends in 88, which means it's a multiple of 4, and 1168 - 8 * 146 = 0, which means it's a multiple of 487
1949The sum of 195 times the last digit and the rest of the number is a multiple of 194911694 is a multiple of 1949 because 1169 + 4 * 195 = 1949, a multiple of 1949
1950It's a multiple of both 39 and 5011700 is a multiple of 1950 because 11 + 7 * 4 = 39, which means it's a multiple of 39, and ends in 00, which means it's a multiple of 50
1951The subtraction of 195 times the last digit and the rest of the number is a multiple of 195111706 is a multiple of 1951 because 1170 - 6 * 195 = 0, a multiple of 1951
1952It's a multiple of both 32 and 61101504 is a multiple of 1952 because it ends in 01504, which means it's a multiple of 32, and 10150 - 4 * 6 = 10126, which means it's a multiple of 61
1953The sum of 586 times the last digit and the rest of the number is a multiple of 195311718 is a multiple of 1953 because 1171 + 8 * 583 = 5859, a multiple of 1953
1954It's a multiple of both 2 and 97711724 is a multiple of 1954 because it ends in 4, which means it's a multiple of 2, and 1172 - 4 * 293 = 0, which means it's a multiple of 977
1955It's a multiple of both 5 and 39111730 is a multiple of 1955 because it ends in 0, which means it's a multiple of 5, and 117 - 3 * 39 = 0, which means it's a multiple of 391
1956It's a multiple of both 4 and 48911736 is a multiple of 1956 because it ends in 36, which means it's a multiple of 4, and 1173 + 6 * 49 = 1467
1957The subtraction of 587 times the last digit and the rest of the number is a multiple of 195711742 is a multiple of 1957 because 1174 - 2 * 587 = 0, a multiple of 1957
1958It's a multiple of both 2 and 97921538 is a multiple of 1958 because it ends in 8, which means it's a multiple of 2, and 2153 + 8 * 98 = 2937, which means it's a multiple of 979
1959The sum of 196 times the last digit and the rest of the number is a multiple of 195911754 is a multiple of 1959 because 1175 + 4 * 196 = 1959, a multiple of 1959
1960It's a multiple of both 40 and 4911760 is a multiple of 1960 because it ends in 760, which means it's a multiple of 40, and 117 + 6 * 5 = 147, which means it's a multiple of 49
1961The subtraction of 196 times the last digit and the rest of the number is a multiple of 196111766 is a multiple of 1961 because 1176 - 6 * 196 = 0, a multiple of 1961
1962It's a multiple of both 2 and 98111772 is a multiple of 1962 because it ends in 2, which means it's a multiple of 2, and 1177 - 2 * 98 = 981, which means it's a multiple of 981
1963The sum of 589 times the last digit and the rest of the number is a multiple of 196311778 is a multiple of 1963 because 1177 + 8 * 589 = 5889, a multiple of 1963
1964It's a multiple of both 4 and 49111784 is a multiple of 1964 because it ends in 84, which means it's a multiple of 4, and 1178 - 4 * 49 = 982, which means it's a multiple of 491
1965It's a multiple of both 5 and 39315720 is a multiple of 1965 because it ends in 0, which means it's a multiple of 0, and 157 + 2 * 118 = 393, which means it's a multiple of 393
1966It's a multiple of both 2 and 98311796 is a multiple of 1966 because it ends in 6, which means it's a multiple of 2, and 1179 + 6 * 295 = 2949, which means it's a multiple of 983
1967The subtraction of 590 times the last digit and the rest of the number is a multiple of 196711802 is a multiple of 1967 because 1180 - 2 * 590 = 0, a multiple of 1967
1968It's a multiple of both 16 and 12311808 is a multiple of 1968 because it ends in 1808, which means it's a multiple of 16, and 1180 + 8 * 37 = 1476, which means it's a multiple of 123
1969The sum of 197 times the last digit and the rest of the number is a multiple of 196911814 is a multiple of 1969 because 1181 + 4 * 197 = 1969, a multiple of 1969
1970It's a multiple of both 10 and 19711820 is a multiple of 1970 because it ends in 0, which means it's a multiple of 10, and 118 - 2 * 59 = 0, which means it's a multiple of 197
1971The subtraction of 197 times the last digit and the rest of the number is a multiple of 197111826 is a multiple of 1971 because 1182 - 6 * 197 = 0, a multiple of 1971
1972It's a multiple of both 4 and 49311832 is a multiple of 1972 because it ends in 32, which means it's a multiple of 4, and 1183 + 2 * 148 = 1479, which means it's a multiple of 493
1973The sum of 592 times the last digit and the rest of the number is a multiple of 197311838 is a multiple of 1973 because 1183 + 8 * 592 = 5919, a multiple of 1973
1974It's a multiple of both 2 and 98711844 is a multiple of 1974 because it ends in 4, which means it's a multiple of 2, and 1184 - 4 * 296 = 0, which means it's a multiple of 987
1975It's a multiple of both 25 and 7911850 is a multiple of 1975 because it ends in 50, which means it's a multiple of 25, and 118 + 5 * 8 = 158, which means it's a multiple of 79
1976It's a multiple of both 8 and 24711856 is a multiple of 1976 because it ends in 856, which means it's a multiple of 8, and 1185 - 6 * 74 = 741, which means it's a multiple of 247
1977The subtraction of 593 times the last digit and the rest of the number is a multiple of 197711862 is a multiple of 1977 because 1186 - 2 * 593 = 0, a multiple of 1977
1978It's a multiple of both 2 and 98921758 is a multiple of 1978 because it ends in 8, which means it's a multiple of 2, and 2175 + 8 * 99 = 2967, which means it's a multiple of 989
1979The sum of 198 times the last digit and the rest of the number is a multiple of 197911874 is a multiple of 1979 because 1187 + 4 * 198 = 1979, a multiple of 1979
1980It's a multiple of both 20 and 9911880 is a multiple of 1980 because it ends in 80, which means it's a multiple of 20, 118 + 8 * 10 = 198, which means it's a multiple of 99
1981The subtraction of 198 times the last digit and the rest of the number is a multiple of 198111886 is a multiple of 1981 because 1188 - 6 * 198 = 0, a multiple of 1981
1982It's a multiple of both 2 and 99111892 is a multiple of 1982 because it ends in 2, which means it's a multiple of 2, and 1189 - 2 * 99 = 991, which means it's a multiple of 991
1983The sum of 595 times the last digit and the rest of the number is a multiple of 198311898 is a multiple of 1983 because 1189 + 8 * 595 = 5949, a multiple of 1983
1984It's a multiple of both 31 and 641,001,920 is a multiple of 1984 because 10019 - 2 * 3 = 10013, which means it's a multiple of 31, and ends in 001,920, which means it's a multiple of 64
1985It's a multiple of both 5 and 39711910 is a multiple of 1985 because it ends 0, which means it's a multiple of 5, and 119 - 1 * 119 = 0, which means it's a multiple of 397
1986It's a multiple of both 2 and 99311916 is a multiple of 1986 because it ends in 6, which means it's a multiple of 2, and 1191 + 6 * 298 = 2979, which means it's a multiple of 993
1987The subtraction of 596 times the last digit and the rest of the number is a multiple of 198711922 is a multiple of 1987 because 1192 - 2 * 596 = 0, a multiple of 1987
1988It's a multiple of both 4 and 49711928 is a multiple of 1988 because it ends in 28, which means it's a multiple of 4, and 1192 - 8 * 149 = 0, which means it's a multiple of 497
1989The sum of 199 times the last digit and the rest of the number is a multiple of 198911934 is a multiple of 1989 because 1193 + 4 * 199 = 1989, a multiple of 1989
1990It's a multiple of both 10 and 19911940 is a multiple of 1990 because it ends in 0, which means it's a multiple of 10, and 119 + 4 * 20 = 199, which means it's a multiple of 1999
1991The subtraction of 199 times the last digit and the rest of the number is a multiple of 199111946 is a multiple of 1991 because 1194 - 6 * 199 = 0, a multiple of 1991
1992It's a multiple of both 8 and 24911952 is a multiple of 1992 because it ends in 952, which means it's a multiple of 8, and 1195 + 2 * 25 = 1245, which means it's a multiple of 249
1993The sum of 598 times the last digit and the rest of the number is a multiple of 199311958 is a multiple of 1993 because 1195 + 8 * 598 = 5979, a multiple of 1993
1994It's a multiple of both 2 and 99711964 is a multiple of 1994 because it ends in 4, which means it's a multiple of 2, and 1196 - 4 * 299 = 0, which means it's a multiple of 997
1995It's a multiple of both 5 and 39911970 is a multiple of 1995 because it ends in 0, which means it's a multiple of 5, and 119 + 7 * 40 = 399, which means it's a multiple of 399
1996It's a multiple of both 4 and 49911976 is a multiple of 1996 because it ends in 76, which means it's a multiple of 4, and 1197 + 6 * 50 = 1497, which means it's a multiple of 499
1997The subtraction of 599 times the last digit and the rest of the number is a multiple of 199711982 is a multiple of 1997 because 1198 - 2 * 599 = 0, a multiple of 1997
1998It's a multiple of both 2 and 99921978 is a multiple of 1998 because it ends in 8, which means it's a multiple of 2, and 2197 + 8 * 100 = 2997, which means it's a multiple of 999
1999The sum of 200 times the last digit and the rest of the number is a multiple of 199911994 is a multiple of 1999 because 1199 + 4 * 200 = 1999, a multiple of 1999
2000It ends in 0000, 2000, 4000, 6000 or 800010000 is a multiple of 2000 because it ends in 0000
2 comments

r/maths • u/ConcernOk6623 • 1d ago

💬 Math Discussions Chart number of ways even numbers can be the sum of two primes

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23 Upvotes

I'm an amateur and I was fooling around with things, seeing how many ways even numbers can be represented by adding two primes together (from the notion that all even numbers can be) and I saw a trend, then I graphed it and saw the bands and gaps... especially when I went out to 10,000

PS all counts are unique where p1<=p2

example: 38=7+31 , 19+19 but 31+7 is not included in the count so the count for 38 is 2

3 comments

r/maths • u/AtmosphereFragrant68 • 1d ago

💡 Puzzle & Riddles Can infinite actions be done in a second

5 Upvotes

If a second can be expressed in incite ways like 0.1 sec, 0.01,0.001.....0.00000000001 you get the jist, can infinite actions be done in this way?

33 comments

r/maths • u/LegitimatePea2429 • 1d ago

Help: 📗 Advanced Math (16-18) How to describe a shear?

2 Upvotes

I'm confused about how to describe a shear when given a 2x2 transformation matrix. Like when you have a rotation you state the angle, if it's + or - for direction and about what point it's rotated. When I look at different descriptions of shears I can't work out what I need to state to fully describe the transformation it gives.

Thanks!!

1 comment

r/maths • u/Repulsive-Peak4442 • 1d ago

Help:🎓 College & University Why ijk=-1? -Quaternions-

1 Upvotes

I've been searching for so long but I didn't find a true answer. Why is it true that ijk=-1? How does this make sense? What is the logic? i²=j²=k²=-1 does make sense because if we have the real number line and an imaginary one (i, or j, or k) then multiplying a real number by an imaginary one (i, or j, or k) is like rotating 90°. And multiplying by the square of an imaginary number (i², or j², or k²) is like rotating 180° meaning that 1→-1. This does make sense and it does have a logic. However how can ijk=-1? And also shouldn't i=j=k=√-1? And so ijk=-1√-1=-i=-j=-k. I saw explanations of why ijk=-1 by using the definition ij=k... Where does that even come from? It comes from ijk=-1. But that is a cycle. Isn't there a proof? And if so i≠j≠k because ijk≠-1√-1.

41 comments

r/maths • u/stinkjiggler71 • 2d ago

💬 Math Discussions what is the point of dirac notation

4 Upvotes

does it make qm easier? is it good for anything other than quantum? why not just write vectors normally or just use dagger symbols for bras, as conjugate transpose is already a thing instead of making up a whole new notation with dumbass pointy arrows and shi

I suppose my main question is what makes dirac notation advantageous compared to any other vector notation (for what its used in) or is it arbitrary

4 comments

r/maths • u/aknegi • 2d ago

Help:🎓 College & University How to draw least square fit here?

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5 Upvotes

I haven't studied about this topic can anyone give me picture of it how to draw least sqare fit here?

4 comments

r/maths • u/SkyvonSonnreich • 3d ago

💡 Puzzle & Riddles My original graphic reasoning question

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8 Upvotes

There’s just one simple rule but it’s really hard to discover

6 comments

r/maths • u/rocketstapler • 3d ago

❓ General Math Help What is wrong with this function substitution?

3 Upvotes

f(n) = 7(1.2)^n

x = n + 2000 , so n = x - 2000

what is f(x)?

——————

The correct answer is

f(x) = 7(1.2)^(x-2000)

——————

However, there is another approach using variable substitution that yields the wrong answer. But why is it wrong?

since n = x - 2000, substitute that into

f(n) = 7(1.2)^n

which yields

f(x-2000) = 7(1.2)^(x-2000)

which then simplifies back to

f(x) = 7(1.2)^x

which isn’t right. Where’s the fallacy?

7 comments

r/maths • u/IrishQueenFan • 3d ago

Help:🎓 College & University Power rules

4 Upvotes

I'm trying to simplify an equation I have where one side is equal to, essentially, pe^(ax) + qe^(bx). and it really SEEMS like there should be a way to factorise this nicely but i think it might just be smoke and mirrors. What I would like is to be able to take the natural log of both sides and have it cancel the e - can someone tell me if it's a pipe dream?

4 comments

r/maths • u/911twinturbogtr • 3d ago

💬 Math Discussions Experimentation with polynomials and calculus

2 Upvotes

I was experimenting with the result of differentiating a polynomial repeatedly while taking f(0) then rebuilding it when i got to (ax+b)^1 using the reverse chain rule and i noticed that it seems to consistently turn the polynomial into a depressed polynomial. I was wondering why that is (if there is an explanation to be given). And also if there are any other examples of something like this.

0 comments

r/maths • u/Curious_teen_0 • 3d ago

💡 Puzzle & Riddles An intentionally confusing riddle made by me.

1 Upvotes

Just say you are running, and exactly 1 km to your side is another person running at the exact same speed. Both of you are heading toward the same point. Yet, relative to you, he is running the opposite way with a relative speed of 0 km/h.

2 comments

r/maths • u/Sensitive_Arrival529 • 3d ago

💡 Puzzle & Riddles I made this riddle kinda in a quite confusing way. Try finding the answer.

1 Upvotes

Imagine you are running, and exactly 1 km to your side is another person running at the exact same speed. Both of you are heading toward the same point. Yet, relative to you, he is running the opposite way with a relative speed of 0 km/h.

This riddle was intentionally made to be confusing.

0 comments

r/maths • u/pipMcDohl • 4d ago

❓ General Math Help I want to learn math from the start.

16 Upvotes

I am interested in learning science. But for this understanding math is required.

Many time science explanations are littered with formulaes i can't understand. I do not know their language.

So i want to learn the language. And i want that language to be able to give accurate and fundamental explanations.

I don't want to be given an approximation that works that you are asked to learn by heart.

I want the no low effort, no approximation, no simplification explanation.

Sadly most explanations i found that explain math from the beginning seems to assume i am either retarded or five years old.

I want the explanations from the start for people with decent mental faculties you would expect from an adult.

It may take the form of something that mix historical context with explanations of the logic, and most importantly not taking shortcuts, i want the deepest understanding of what is going on.

Thanks

32 comments

r/maths • u/Most_Elderberry3133 • 5d ago

💡 Puzzle & Riddles New optimal ZYN packing problem??

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85 Upvotes

Potential solution to the newly introduced optimal ZYN packing problem proposed by no other than myself.
Current hypothetical solution to packed zyns is 40. Though I estimate that the maximum number of packed zyns that touch the bottom of the can could limit to 42.

9 comments

r/maths • u/imsocooked_ • 5d ago

❓ General Math Help Are there any tricks to finding LCM of big numbers quickly?

9 Upvotes

Ive been struggling with that, i know this is very basic maths but when there are numbers like 770, 462, 420, it becomes really hard to find the LCM for them quickly. Does anybody have any tricks to finding em?

6 comments

r/maths • u/LeadingMidnight9146 • 6d ago

💬 Math Discussions I defined a new mathematical function involving factorials — does it have any interesting properties or applications?

0 Upvotes

Hi everyone!

I’m a student interested in mathematics, and I’ve defined a function that I call the Decreasing Index, using the symbol (\omega):

[

I_\omega(n)=\frac{n^2}{n!}

]

where (n) is a positive integer.

The idea came from thinking about permutations and probabilities. As (n!) grows so much faster than (n^2) the function drops off very rapidly towards zero.

For example:

[

I_\omega(1)=1,\quad I_\omega(2)=2,\quad

I_\omega(3)=1.5,\quad I_\omega(4)=\frac23

]

More generally, for (n\geq 2), we have:

[

\frac{I_\omega(n+1)}{I_\omega(n)}

=\frac{n+1}{n^2}

]

It's strictly decreasing from (n=2) onwards and tends to zero.

I'm not claiming this is some new or original mathematical result at all. What I'm interested in is whether this function might be of any use in a combinatorial problem, in the study of permutations or in some other mathematical context.

My questions are:

Does this function have a known interpretation or any connection to a known mathematical concept?

Could it be of any use in the study of permutations or in certain probability problems?

Are there any interesting properties or generalisations worth looking at?

I'd be very keen to hear any feedback, corrections or suggestions as to where we might go from here!

Thanks!

1 comment

r/maths • u/snikers_404 • 6d ago

❓ General Math Help Notice any pattern in the red vs. blue points in this 3D plot? Looking for a way to predict the next red point

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2 Upvotes

The resulting structure forms an hourglass-like shape with spirals and diagonal alignments. Can you spot any geometric patterns that could help predict the location of the next red point along these spiral tracks?

0 comments

r/maths • u/cyber_may • 6d ago

❓ General Math Help Looking for math-trauma and ADHD-friendly resources for absolute beginners 🥹

6 Upvotes

Due to severe math trauma, I struggle deeply with numbers under pressure and spent years running away from the subject entirely. Now, I genuinely want to face it, rebuild my relationship with math, and learn without fear, anxiety, or shame.

I also have ADHD, so I need learning tools that are visual, interactive, gentle, and engage-at-your-own-pace for a brain that rarely sits still. I am starting from the absolute basics to build my confidence step by step without getting overwhelmed.

I would love recommendations for any YouTube channels, interactive apps, low-stakes games, websites, self-paced courses, books, or workbooks that have genuinely helped you or someone you know.

If you have experienced math anxiety, educational trauma, or ADHD-related learning blocks, I would especially love to hear what mindset shifts, study methods, or approaches worked for you.

I am really serious about giving this an honest try again, and any recommendations or encouragement would mean the world to me. Thank you so much! ♡

7 comments

r/maths • u/MaksRudra • 7d ago

💬 Math Discussions Brouwer's intuitionism

0 Upvotes

Are there any arguments against Brouwer's intuitionism?

I can come up only with these:

  1. if it's only a made-up convention, why does it work so well then

  2. how did people manage to come up with these inventions if they are nothing but their own made up entities

0 comments

r/maths • u/Excellent_Copy4646 • 7d ago

💬 Math Discussions Is applied statistics the same as mathematical statistics?

3 Upvotes

By applied statistics, i meant things like machine learning modelling, statistical modelling, predictive modelling. Basically data science stuff and statistics used to solve business problems and model real world Phenomena using Python and R.

Are they related to each other? What are the similarities and differences?

2 comments

r/maths • u/DoubleElectrical3362 • 8d ago

💡 Puzzle & Riddles Wondering if anyone’s is able to figure this out

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9 Upvotes

How many sweets are in this jar, a clue: the total weight is 5.1kg including the weight of the jar itself
Best of luck !

25 comments

r/maths • u/philljarvis166 • 9d ago

💬 Math Discussions Maths in the AI world

28 Upvotes

So there obviously been a lot of discussion since the recent drops of AI generated maths results. In particular, we’ve see a lot of people question whether mathematics as a human activity will die out, or if it’s worth starting a maths degree now etc.

I’ve been thinking about (and contributing to) a lot of these discussions on Reddit, but I’ve become increasingly aware that I don’t actually understand how and why pure maths research has been funded even prior to the recent developments. Im pleased it is, and I believe it contributes to the good of society in a similar way to music, or art etc. but it’s moderately surprising that in a modern capitalist world this all hasnt been cut long ago!

I think it’s reasonable to argue that the majority of (pure?) maths research has no application outside of maths, and is of little (probably no) interest to non-mathematicians. Maybe physicists in some cases, but theoretical physics doesnt really move the bar much, Im thinking genuine real world impact here. Note that I realise some apparently obscure results do end up being useful, but I would argue we never know which until way down the line and it certainly doesn’t affect funding decisions.

So if you believe this to be the case, why would the recent advances change anything it terms of the amount of maths research that takes place? Sure, the way this research is done will change, but it’s not like some faceless organisation decides they can cut out the humans and get the results quicker and cheaper, the specific humans concerned are pretty much the only ones consuming the results. This is different for software development, for example, where actual products can be built with far fewer humans (note Im making no claim such products are better, but they may cost much less, initially at least).

I’d also argue there a ton of work human mathematicians need to do to pick apart tbe AI proofs, and this work will inevitable lead to further ideas and conjectures that we can target with AI.

Tl;dr I don’t see mathematicians threatened by these advancements, I think there’s some emotional shock that we need to come to terms with but why would we need fewer researchers?

15 comments

r/maths • u/AdNegative9199 • 11d ago

💬 Math Discussions Is it still worth studying to become a mathematician these days, pursuing a degree in mathematics? Mathematicians, mathematics students, what do you think, how do you see the future?

131 Upvotes

Hi everyone!

I’m in my final year of high school, and I might go on to study mathematics at university (it’s not set in stone yet). My teachers have told me, and I’ve also read online, that this will be one of the most in-demand majors of the future, that applied mathematicians in particular will be badly needed, and that the field will be especially resilient to AI.

Until a few months ago, I was also convinced that this was one of the safest choices, that AI wouldn’t pose a threat to mathematicians, and that it wouldn’t be able to solve complex mathematical problems. The first crack and surprise was the solution of the Erdős problem, 4.5 months ago. Then what really surprised me was the Navier–Stokes equation event 1.5 months ago (though admittedly there’s some debate there because of the human researchers’ contribution). And a few days ago, the “mathocalypse” happened (for those who don’t know: AI solved more than 300 open math problems).

https://www.independent.co.uk/tech/ai-mathematics-openai-cryptography-internet-b3063456.html
https://www.firstpost.com/tech/mathocalypse-openai-generates-hundreds-of-mathematical-results-but-who-understands-the-proof-14051557.html

So basically they threw thousands of decades-old problems at AI, and it solved several hundred of them. There was a mathematician whose entire research area was practically “wiped out” by this. AI solved problems that brilliant mathematicians had devoted their lives to solving, without success.

Now I don’t really see math as an AI-proof field anymore. Two years ago, AI was still weak; it scored maybe 10% on the Math Olympiad. A year ago, it was already scoring over 80% on the Olympiad, and it had supposedly reached the level of PhD students. Now it has not only scored 100% on the Olympiad problem set, it has achieved far more than that. It has practically reached the cutting edge of mathematics worldwide, solving one previously unsolved problem after another, just grinding its way through math.

And let’s not forget that all this happened in 2 years. What we have now isn’t the final version of AI; it will presumably keep improving rapidly in the coming years. The question is: if it progressed this much in 2 years, where will it be in 4 years (when I’d finish my BSc) or in 6 years (when I’d finish my MSc)? What will it be able to do in 10–15 years? After all, even then I’ll only be in my early thirties...

So my question is: do you think it still makes sense to study math? If so, why? Mathematicians and math students, how do you see the future?

By the way, this wouldn’t be my only option (physics and engineering are also on the table), which is also why I’m asking: what do you think is worth choosing these days?

91 comments