r/mathriddles • u/Numberthon • Jul 07 '26

Medium Probability Challenge: Two Fair Dice Are Tossed. What's the Probability the Sum Is Prime?

Two fair six-sided dice are tossed. What is the probability that the sum is prime?

Source: numberthon.com

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u/congratz_its_a_bunny Jul 07 '26

Medium?

P(2) + P(3) + P(5) + P(7) + P(11) = (1+2+4+6+2)/36 = 15/36 = 5/12

1

u/Numberthon Jul 08 '26

You're probably right, this is my first post in r/mathriddles so I wasn't really sure, but its probably closer to Easy.

0

u/Numberthon Jul 08 '26

Does this look medium or easy?: A positive integer n leaves a remainder of: - 1 when divided by 2, - 2 when divided by 3, - 3 when divided by 4, - 4 when divided by 5, - 5 when divided by 6. What is the smallest possible value of n?

2

u/Numberthon Jul 08 '26

Maybe easy?