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math is hard (lemm.ee)
submitted 1 month ago by [email protected] to c/[email protected]
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[-] [email protected] 117 points 1 month ago

Intuitively speaking, how many times does half of a thing fit into a quarter of a thing? The answer is, exactly one half time.

[-] [email protected] 98 points 1 month ago

How many halves fit into a quarter? Half of them

[-] [email protected] 19 points 1 month ago

That's exactly how I think of it, so strange someone downvoted you

[-] [email protected] 66 points 1 month ago* (last edited 1 month ago)

✅ Math is hard

❌ This math is hard

[-] [email protected] 34 points 1 month ago

0.25 / 0.5 = 0.5
0.25 = 0.5 × 0.5
1/4 = 1/2 × 1/2

[-] [email protected] 33 points 1 month ago

p/q=q

So q=√p

Works with a lot of numbers ☝🏻🤓

[-] [email protected] 11 points 1 month ago

Ehhh |q| = √p but close enough

[-] [email protected] 3 points 1 month ago

If q=√p then -q=√p also.

[-] [email protected] 30 points 1 month ago

This is why "divide by half" and "divide in half" are two different things

[-] [email protected] 24 points 1 month ago

It won’t keep you up if you just think of Divide as just multiplying by the fraction

[-] [email protected] 5 points 1 month ago

Yeah I was gonna comment that 0.25*(1/0.5) = 0.5 doesn't look nearly as weird

[-] [email protected] 8 points 1 month ago* (last edited 1 month ago)

I didn’t specify fully, but I was just thinking 1/4 * 2/1

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[-] [email protected] 4 points 1 month ago

The math looks perfectly fine. But when people phrase "half of a quarter" I think they have (1/2)*(1/4) in mind, instead of 0.25/0.5

[-] [email protected] 4 points 1 month ago

But this isn't "half of a quarter" this is "the reciprocal of a half, of a quarter"

Half of a quarter is 0.25/2 or 0.25*1/2

[-] [email protected] 5 points 1 month ago

I know, but to me this meme doesn't make sense to me unless I assume the person reading the math Expression is interpreting its real world application.

25 / 5 = 5 and nobodies head exploded. That's just evaluating a math Expression. .25 / .5 = .5 is the same. It's not a "my brain can't comprehend how to evaluate expressions" as the meme suggests.

However, if someone who doesnt do much algebra thought to themselves "I need half of a quarter", then I could understand why their brain might "hurt" as the meme suggests, for a similar reason why adding 20 degree Celsius water to 20 degree Celsius water doesn't make 40 degree Celsius wate

I'm probably reading into it too much, but the meme just doesn't feel like a "mind fuck that keeps me up at night". I'm looking for reasons to try and explain it, but it's just a math expression at the end of the day

[-] [email protected] 2 points 1 month ago

I think you nailed the confusion in this meme.

To simplify: it's confusing that ½ = 0.5, but 1/2 ≠ 1/0.5

[-] [email protected] 2 points 1 month ago

I think the meme is an exaggeration of the situation for comedic effect. It just looks silly at first glance, I don't believe the OP is kept up at night by this, and is rather making a remark about how it doesn't instantly feel intuitive as a result (to use the 20 Celsius water example, its the same kind of momentary "wtf?" as 40 Celsius water not being twice as hot as 20 Celsius water. After a moment you remember "oh derp yeah we're missing 273.15 kelvin in this picture lol")

[-] [email protected] 22 points 1 month ago

If you give half a person a quarter of a thing, how much would you be giving a full person? That's right baby, half a thing. Don't sweat it.

[-] [email protected] 18 points 1 month ago

I worry that people who can get onto the internet find fractions a challenge.

[-] [email protected] 3 points 1 month ago* (last edited 1 month ago)

I don't think this was shared because people are finding it a "challenge" it just looks funny.

It takes all of a few seconds for your actual mathematical processing to kick in and you go "oh yeah duh" but its just a funky little string of numbers.

It lives in the same camp as how none of the >3 whole multiples of 17 feel like multiples of 17. 68? Preposterous.

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[-] [email protected] 14 points 1 month ago

x / sqrt(x) = sqrt(x)

Damn who would've thought?

[-] [email protected] 14 points 1 month ago* (last edited 1 month ago)

Divide by 1/2 or multiply with 2/1. It's an equivalent transformation.

[-] [email protected] 12 points 1 month ago

I just think of division as how many times the right expression fits inside the left expression. 0.5 fits into 0.25 only 0.5 aka 1/2 times, because only half of it fits.

[-] [email protected] 10 points 1 month ago

Precisely this. The people not getting the OP are why Common Core was developed.

[-] [email protected] 11 points 1 month ago
[-] [email protected] 11 points 1 month ago

The numbers between zero and one are where all of the fun is!

[-] [email protected] 10 points 1 month ago

1×2=2

Wow. Much brain. Maths wow.

[-] [email protected] 9 points 1 month ago

A quarter is one half of one half. Makes perfect sense.

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[-] [email protected] 8 points 1 month ago* (last edited 1 month ago)
[-] [email protected] 5 points 1 month ago

I think, it is the real world logic that makes it hard to grasp. If you divide something with something small it becomes bigger. Mathematically it's easy and makes sense, but it it's somehow not intuitive. Especially for young me :)

[-] [email protected] 3 points 1 month ago

That's the same as 2/2=1 3/3=1 268/268=1 ...

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[-] [email protected] 7 points 1 month ago

This just comes down to the fact that "dividing by a fraction is the same as multiplying by the inverse of the fraction" is an easy rule to follow but not particularly intuitive. In natural language, when most people hear "divide by half" they're actually picturing "divide by two" in their head.

[-] [email protected] 5 points 1 month ago

This don't avoid to sleep not even for 1/2 second. But pick any number. If that number is even, divide it by 2. If it's odd, multiply it by 3 and add 1. Now repeat the process with your new number. If you keep going, you'll eventually end up at 1.

[-] [email protected] 13 points 1 month ago
[-] [email protected] 8 points 1 month ago* (last edited 1 month ago)

Yes, but everyone tried since a century to find a number with which it don't work, good to avoid sleep.

[-] [email protected] 2 points 1 month ago

Any positive number?

[-] [email protected] 5 points 1 month ago* (last edited 1 month ago)

It’s going to be okay:

Edited to add this: Singapore math insists however, that we eliminate the use of visuals in describing arithmetic within the rationals. They encourage that users of common core rely upon the number line, and solely the number line for thorough and most mathematically sound representations of arithmetic, even when involving the division of fractions.

For those not up to speed to with common core, remember how the teacher used to draw a diagram of a bunny hopping from one integer to the next integer to represent adding given integers, such as 4+3, or -2+1? Imagine that representation being used with problems like 1/7 divided by 5/49, and no decimal approximation is allowed. It’s fascinating and truly something to appreciate from the standpoint of someone who truly loves mathematics. I think it makes for great discussions amongst math graduates like myself, and other math enthusiasts. What does that mean for those who are not so enthused? Sometimes it means the teacher receives death threats from angry students. You can’t make everyone happy.

[-] [email protected] 3 points 1 month ago

I’m not sure I completely agree with the number-line-only approach, but I’m definitely sympathetic to it. It reinforces the idea that fractions are numbers like any other numbers, and not pieces of pizza.

[-] [email protected] 3 points 1 month ago

I get that. I like the number line approach, and respect it, but I have also observed seasoned math coaches fumble the visual explanation of a division by fractions problem where the numerators and denominations were relatively prime. As soon as the guy had drawn the first fraction and began to say, “we’d multiply by the recipro-…”, I could tell it was going to be long problem. He just stood there, and then asked, “well, how would I go about explaining the ‘keep change flip’, if you will?” He ended the problem by saying he might just explain that the distance drawn for the first fraction needs to be repeated on the other side of the fraction to show the multiplication by the denominator of the second fraction, and then that distance could be broken into parts to demonstrate the division by the previous numerator of the second fraction.

Basically he ended the problem by saying, “let’s just reflect it! Then we can break it up.” There wasn’t really a sound justification for the reflection piece of the process, other than saying, “we need to multiply by the reciprocal of the second fraction, so we’ll just have to multiply by its denominator it had, prior to flipping it.”

That was the quietest meeting I have ever seen amongst that group of adults.

[-] [email protected] 3 points 1 month ago

Multiplication of x times 6:

x * 6 = 1/2 x * 10 + x

This can sometimes be a shortcut for numbers that are easier to divide by 2 than to multiply by 6.

Take half as tens and add the number.

6 * 6 = 30 + 6 = 36

8 * 6 = 40 + 8 = 48

150 * 6 = 750 + 150 = 900

320 = 1600 + 320 = 1920

Etc.

Sleep well.

[-] [email protected] 2 points 1 month ago* (last edited 1 month ago)

So an extension of the x * 5 = x/2 * 10 shortcut

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[-] [email protected] 3 points 1 month ago* (last edited 1 month ago)

2^-2 * (2^-1)^-1 = 2^-2 * 2^(-1 * -1) = 2^(-2 + -1 * -1) = 2^(-2 + 1) = 2^-1 = 1/2 = 0.5

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this post was submitted on 14 May 2024
437 points (88.5% liked)

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