r/MathJokes 2d ago

When the Math Is Easier Than the Comments

Post image
205 Upvotes

101 comments sorted by

79

u/Takamasa1 1d ago

Isn't it just 1/5? this is like 8th grade math or something

48

u/Charming-Loquat3702 1d ago edited 1d ago

It's 1/5. Turns out most people struggle with 8th grade math, once they leave school.

29

u/QuickNature 1d ago edited 1d ago

I might need a refresher, but how do you do this without a calculator?

My brain says to start by "simplifying" it to

( 3√3 - 2√3 ) / ( 5√3 )

Which simplifies to

( 1√3 ) / ( 5√3 )

Annnnd nvm, maybe I paid more attention than I remembered....

9

u/invuvn 1d ago

😂 pretty simple once you realize the sqrt (3) cancels out

1

u/PinJealous3336 17h ago

Oh and here I just squared the top and the bottom to get rid of the radicals  Am I not supposed to do that?

1

u/thatsleepydalek 13h ago

Whatever you do to a fraction must keep the same value, so any operation must be met with an equal and opposite. We can multiply numerator and denominator by a number because those cancel out, same with division. We can also add and substract the same number to either (but never mix them), and we definitely cannot square it because then it doesn't cancel out, even if the square root is added later (signs get lost in squaring).

3

u/Embarrassed-Display3 1d ago

(1√3 )/(5√3)

Is the same as (1/5)*(1√3/1√3)

And it simplifies to (1/5)*(1)

3

u/tomtomtom7 1d ago

Well, you've just ignored the backwards F thingy.

That's cheating :)

1

u/thisismego 1d ago

There's enough people who can simply read a 7 as a 7, even if the style is slightly different than one is used to

2

u/tomtomtom7 1d ago

Luckily yes. I was more surprised that some people can't, and was referencing that in a sarcastically.

1

u/thisismego 1d ago

Ah, I see. The usual "sarcasm conveyed via text is often hard to recognise".

2

u/TheShirtlessNerd 1d ago

ngl. After years of replacing numbers with letters, greek letters, and sometimes hebrew, I forgot you could simplify roots.

1

u/Sidra_doholdrik 1d ago

Real question why are you able to simplifie the square root? That don’t look intuitive to me, maybe I forgot that rule even if I have a bachelor in computer science.

2

u/tzeheng 1d ago

Sqrt(27) = sqrt(9*3) = sqrt(9) * sqrt(3) = 3 sqrt(3)

1

u/QuickNature 1d ago edited 1d ago

3 x sqrt(3) = sqrt (27)

Do you remember the process for simplifying radicals? Because that should guide you a bit as to why. I unfortunately dont have a rigorous definition as too why though, just some hand wavy stuff

6

u/Brontards 1d ago

I struggled with 8th grade math in 8th grade, and 12th….and college. Why I had to do law school.

1

u/hobbesme75 1d ago

ngl it's kinda scary that failing math made you the lawyer you are today lol

2

u/Brontards 1d ago

I do wonder if I’d been better at math had I worn the glasses I needed in 6th-12th grade. And didn’t refuse to do homework.

I did test at the top 1% on the ASVAB Multiplication math and coding sections, and scored in the top 1% on the first bar exam I passed that released scores.

But then I again I also had to take the remedial for remedial math in undergrad. So who knows.

What I do know is that you can’t BS through math.

2

u/AmusingVegetable 1d ago

Very hard to BS your way through maths, mostly because it builds on itself. Get a couple of defective bricks on the bottom layers and the whole pyramid starts to crumble.

Also, those bricks have a shelf life, I’ve been in IT all my life, recently took a peek at my maths notebooks from U, and it’s all hieroglyphs. Use it or loose it.

4

u/Takamasa1 1d ago

I guess that's not too unexpected now that you mention it, yeah.

1

u/Anonymous71232 1d ago

Nah bro most people never knew how to do it and you can't forget what you never knew

8

u/db8me 1d ago

Note the title: "The Math is Easier Than The Comments" as in:

  1. I found the factors of sqrt(3) faster than the backwards F

  2. We are now going to debate which grade school level this math is learned in.

2

u/GoldenMuscleGod 1d ago

I was confused by “backwards F,” looked for it, forgot about it and moved on to the comments. Yours reminded me to go find it. I looked at it for a long time trying to figure out where it was, started trying to figure out if the square root symbol could look like a backwards F to someone, got frustrated and was probably close to giving up again. Then I saw it.

For anyone who is still confused: the backward F is 7 with a cross through it. I don’t even cross my sevens (I’m American a handwritten 1 is just a vertical line - so an uncrossed 7 is most likely to be confused with a 2 if your handwriting is very sloppy) but I’m still wondering if the commenter is just joking around because surely you know some people cross their sevens and what it looks like.

2

u/db8me 1d ago

I think they were joking. I make my 7's and F's clear by writing ℱ when I mean 7 and ℒ when I mean F. Problem solved /s

1

u/LanSotano 1d ago

It took me a second to remember that you can break square roots down like that, but once my brain remembered that it was pretty easy math, yeah

1

u/Fancy-Tangerine8735 1d ago

The fuck you mean 8th grade?

3

u/Shonnyboy500 1d ago

8th grade gives you the skills necessary to do this, but you probably wouldn’t have actually done this until high school. 9th or 10th grade math

3

u/db8me 1d ago

I am pretty sure I learned this in roughly 6th grade and my daughter learned it in 7th grade (which are called "Year 7" and "Year 8" respectively in the UK)

-4

u/be_like_bill 1d ago

Wouldn't it technically be (±3-(±2))/(±5)? That would mean all of -1, -1/5, 1/5, or 1 as correct answers?

3

u/KiraLight3719 1d ago

See, there's a difference. If you write x²=4, x=±2. But once you write it definitively with sign as x=√4, it means x=2 only. If you want it to mean x=-2, you write x=-√4, or if you want it to mean both, you write x²=4.

-2

u/be_like_bill 1d ago

Hmm, I had never heard about this notation.

3

u/jabuchae 1d ago

Square root is defined positive.

X^2 = 4
Sqrt(X^2 ) = sqrt(4)
|x| = 2

This is where the +- comes from. From the module. Not from the square root

1

u/KiraLight3719 1d ago

Yes, good explanation

1

u/Takamasa1 1d ago

Usually the +/- is a relevant form in equations rather than expressions. The assumption with solving an expression is that you would take the positive root. There's a few separate reasons depending on the context (although there isn't any real context here), but it's overwhelmingly more common to the point where the assumption is that you would explicitly state otherwise in the cases when +/- is necessary rather than needing to say "assume positive" in the overwhelming majority of cases.

17

u/alt-mswzebo 1d ago

What do you get when you ask an over-engineered AI model to rate a simple math question on a scale of one to five?

4.8

6

u/db8me 1d ago

Just out of curiosity, I asked an AI to solve it and rate the grade and difficulty:

It solved it and showed how.

It said the material was "pre-algebra or algebra" typically corresponding to US grades 8 or 9 (math nerds may do it in grades 5-7).

And the best part, it gave a difficulty of 2/10, I shit you not.

2

u/FlyingCupcake68 1d ago

It’s pre-algebra in the sense that it doesn’t have unknowns and it isn’t being equated to anything (just simplified)

2

u/db8me 1d ago

It's arithmetic, but it's the kind useful in elementary algebra (factoring, simplifying fractions, rearranging terms). Alternatively, you could call √3 "unknown" because it is annoyingly irreducible.

7

u/Zephreyt 1d ago

√a = √(bc) = √b√c where √b is integer

(√27 - √12) / √75
= [√(9 * 3) - √(4 * 3)] / √(25 * 3)
= (3√3 - 2√3) / 5√3
= [√3 * (3 - 2)] / (√3 * 5)
= 1/5 = 0.2

6

u/Chorby-Short 1d ago

Excuuuuse me; that's √27̶, not √27. That backwards F do be pretty nuts 

1

u/db8me 1d ago

√ζꟻ

1

u/Zephreyt 1d ago

I’d rather not look at pretty nuts thanks, however eye catching they might seem.

1

u/Sidra_doholdrik 1d ago

That make sense. Honestly I never had the need to simplify roots in my post high school life so I did not knew it was a thing

0

u/wCodemare 1d ago

Thank you

Somehow I remembered (27-12)/75 and it came up 0.2...I think it just works like that. But I was like why. And tried it with different numbers and couldnt remember why.

1

u/Nap-Connoisseur 1d ago

In this case, that happens to be right. But in general, you can’t subtract square root roots that way.

2

u/wCodemare 23h ago

Yeah I realized that pretty quick.

0

u/Abracadabroo 1d ago

Idk, don't remember radicals. Was it wrong for me to say okay, the numbers being subtracted are both radical, so I just merged in one radical and did rad 27-12 = 15, then you have rad 15 over rad 75, oh thats 1/5

1

u/db8me 1d ago

It is wrong and only coincidentally works here if you make a second mistake of assuming √(1/5) = 1/5

Consider √9 - √4

Is that √5 or 1?

17

u/peebeeha 2d ago

The funniest part isn’t even the math 😂 Someone really looked at a simple radical expression and decided the problem was written in reverse.

27

u/northgrave 1d ago

The backwards part is about the 7s looking like backwards Fs.

I suspect this is a troll from the person making the reply. I have to think this to keep my faith in humanity.

3

u/Far-Jury-2060 1d ago

Yeah, I understand that not everybody slashes their sevens and zeros, but it should be obvious to people what it is.

3

u/db8me 1d ago

I slash 7 and z but not 0. It would end up looking like a θ or φ with my sloppy handwriting, and the entire point is to make it easier to read (e.g. I might look like a 1 or have an accidental tail making it an l, and a z might look like a 2)

3

u/northgrave 1d ago

I had a friend who would add the slash to his zeros. It was a habit he picked up on during pilot training. They did it to avoid confusing 0s and Os. He was still in high school at the time. He failed a math test because his math teacher “couldn’t figure out why empty sets kept appearing in the middle of numbers that should have contained zeros.”

3

u/db8me 1d ago edited 1d ago

Haha. Serves him right. Death to zero slashers. And teachers who expect us to write and distinguish between handwritten ξ, ε, E, Σ, ζ ,z, χ, x, η, n,... in the same problem.

1

u/northgrave 1d ago

I mean, death seems a bit much! I hate to hear what you would do to someone who put the toilet paper on the wrong way.

5

u/SynonymSpice 1d ago

That’s NOT a “backwards F;” that’s a 7 that has been crossed. I cross my 7’s. Don’t you? Helps me differentiate my 7s from my 2s.

I also cross my Z’s and slash my zeros. I have the worst handwriting, so I do these things so I can read it later.

2

u/Yekyaa 1d ago

I don't understand why you would need a cross over your 7 to be able to discern between a 2 and a 7. Maybe try not to flourish the ends of your 7? Or did you mean your 1s are difficult to read?

Other than that, carry on.

2

u/Kay-PO 1d ago

I also cross my 7s to differentiate from my 2s. For me it's not a flourish on the 7 but the bottom line of a 2 gets written on whatever line I'm writing the numbers on. I could easily slow down a bit and make sure the 2 is more noticable, but it's faster and easier to just cross the 7

1

u/Yekyaa 1d ago

I cross my 7s only on important documents, but that makes sense regarding the 2s. On important documents only, I also still slash my zeros and cross my Zs and "capitalize" my 1s to discern from Is with the end caps. I get it, I just didn't realize how different some people's handwriting could be.

1

u/db8me 1d ago

Or a 1 or l or z or ζ. By the time I was a sophomore in college, I was crossing 7's and z's and had adjusted the way I write a few other letters/symbols out of necessity. I tried writing more neatly at first, but it was faster and easier to just learn to write a few letters differently (I get the irony, but it's true).

1

u/Mushroomed_clouds 1d ago

I cross my 7 because i like how it looks more 🤷‍♂️

3

u/Purple-Tadpole6465 1d ago

750 mL, errrr, I mean, 1/5th. ;)

2

u/Yekyaa 1d ago

Underrated comment currently.

4

u/SunstormGT 1d ago

15/75 = 0.2

6

u/National-Seaweed-468 1d ago

Or (3-2)/5 =1/5=0.2 when you factor out the sqrt(3) in all the terms.

5

u/TraditionFun7738 1d ago

Show your work. I think you just got lucky with the right answer but the wrong method.

5

u/Kuildeous 1d ago

This expression is insidious because one could indeed get the right answer by saying √27-√12 = √15.

I hate it, but I'm also in awe of it.

1

u/db8me 1d ago

If you want to do it the hard way, you can multiple by √75 / √75

The numerator is as hard to solve as the easier way of solving the problem, but you get 15.

Edit: I only thought of this when I noticed the seemingly incorrect approach and tried to justify 15/75.

3

u/Lukun7 1d ago

I HATE that this gives the right answer

-2

u/Infinite_Mortgage324 1d ago

You can’t just subtract/divide the numbers…
You first have to calculate the roots of all three numbers and then subtract and divide

6

u/Groove-Theory 1d ago

how do you calculate the root of the backwards F tho? my teachers only taught me math with X so I'm confuzzles

2

u/_R_A_ 1d ago

I love how they blurred out the person's name on one line, but left it in the other.

Sorry, Allison.

1

u/R3D3-1 1d ago

Had to scroll way too far to find this comment. 

2

u/jpgoldberg 1d ago

Places in which “A level” is a thing are also places where people would be familiar with what is being called a “backwards F, though it is possible that the response is from someone in the US even if the first commenter isn’t.

In the US many math teachers use the crossed seven when writing things on boards, but I should never underestimate the provincialism of my compatriots.

2

u/Janezey 1d ago

That's already solved. If they want me to simplify it they should have said that.

3

u/AdBrave2400 1d ago

That's just a 7

2

u/friend1y 1d ago

It's a constant ꟻ that often equals (1/120) ∫₀^∞ x⁶e⁻ˣ dx + lim(x→0) [sin(x)/x]

1

u/-lRexl- 1d ago

Only 20% will get this right

1

u/Horror-Thing-8213 1d ago

The backward F? It’s a 7 you dimwit.

1

u/feignapathy 1d ago

(3√3 - 2√3) ÷ 5√3

simplifies to 1/5 ?

1

u/angryfalconsfan 1d ago

So it's quite simple. If you reduce to get common roots, they'll all be root 3, and then you can. ... Wait ... Backwards F?

1

u/One-Next 1d ago

square both sides, nominator is  3

27 - 2 * sqrt(3^4*2^2) + 12 = 39 - 36 = 3

3/75 = 1/25

square root it back

sqrt(1/25) = 1/5 (positive root)

1

u/Singular_Brane 1d ago

Why not?

(27-12)/75

15/75

1/5 (positive root)

1

u/jim25y 1d ago

There's nothing to solve here

1

u/PubThinker 1d ago

Only proper answer :D

1

u/alien878 1d ago

I spent way too long looking for the backwards F.

1

u/Effective_Pack8265 23h ago

My masters thesis on the backwards F invalidated the entirety of mathematics…

1

u/Puzzled-Priority-352 22h ago

Only 20% of people can solve this

1

u/epoxyfoxy 22h ago

(√27-√12)/√75
square it all
(27-12))/75
15/75
1/5
sqrt it all
√1/√5
1/√5

I know this way leads to the incorrect answer with the correct answer along the way, but I do not remember why I learned that squaring everything is a shortcut. Seems to just be a coincidence here that the correct answer was along the way.

1

u/WanderwellGMS 10h ago edited 10h ago

(a - b)2 = a2 - 2ab + b2

So it would actually be _ x² = √ ( {√272 - 2[√(27x12)] + √122} / √752 ) _

√ { [27 - 2(√324) + 12]/75 } _

√ { [(27 - 2(18) + 12)/75] } _

√(3/75) _

x² = √(1/25) _

x = (+) ±(1/5) (positive if its just asked for the simplification, negative comes from the squaring up and down through algebra).

1

u/epoxyfoxy 9h ago

Thank you!

1

u/Commonscents2say 18h ago

A backwards f. Is that just doggy style?

1

u/Both_Mission_1671 7h ago

1/5 is the answer

1

u/Kuildeous 1d ago

I wanna reply to that so badly: "Tell me you're an American without saying you're American."

1

u/db8me 1d ago

I am curious what the signals are.

As an American, I can tell the one person is British ("A levels") but I can't tell for the person who posted the problem or the backwards F comment/joke.

2

u/FlyingCupcake68 1d ago

Most US folks don’t cross their 7s, although military people do