transitive and commutative
this post was submitted on 25 Jun 2026
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In either case I would multiply 5 by 6 and move the decimal. Interesting though.
6 of 50 is 300. % just means 1/100. That's also a good way to think of it.
Let's try this on a sale item. Hmm, let's see, the sign says 25% off $6.99. So that's the same as, let's say, 7% off $25. Oh, yeah, that is much easier. /s
Wait...
So 25% off $100... is 100% off $25! Trollface
I mean if you remove the word off it works. 25% off $100 is $25 100% of 25 is 25 it's still reversible you just let the word off confuse you
You could also make sure to carry “off” to both sides when you swap:
25% off of $100 is 100% of $25 off
Another counter-intuitive percentage fact: A 10 percent discount and a 10 percent fee can be calculated in either order but they don't cancel out.
Example, 90% of (110% of 10) = 110% of (90% of 10). But neither of those is evaluates to 10. They evaluate to 9.9.
For any percentage X, and and base value C, (100 - X)% x ((100 + X)% x C) = (100 + X)% x ((100 - X)% x C) = (100 - (X^2/100))% x C
This one irks me to no end.
Strange Panzers lying in ponds distributing shells is no basis for a system of government…
Surely you don't think supreme executive power derives from a mandate from the masses?
I thought we were an autonomous collective
As opposed to what, a farcical aquatic ceremony?
That was unexpected.
And now for something completely different
No one expects the python imposition!
Everyone’s talking about this math. I’m wondering about the panzer.
They said the water could reach up to 50% of its 1.7 meter height before causing problems, panzer tried calculating 1.7% of 50 meters from head, this is the result.
This is far too useful to be a shitpost.
it's very often not useful. Like, what's 6% of 80? See. Still hard.
Also, with the 6% of 50 example it's easy without using this trick.
What's 6% of 100? 6, right? So cut 100 in half to get to 50, and cut the 6 in half to get the 3. Cut the 50 in half again and cut the 3 in half again, and you'll also know that 6% of 25 is 1.5.
Which also lets you know that 6% of 75 is 4.5. the 3 from the 50, plus the 1.5 from the 25. or just know to split the difference between the 3 at 50 and the 6 at 100.
A lot of math is just tricks for a thinking process.
Good luck explaining your supreme methodology to anyone that isn't a geek.
It's stupid simple..... If you know 6% of one hundred is 6, then you should know 6% of 50 is 3. You just cut each number in half.
I know right. I even open the calculator app to verify before committing to memory this nugget.
Barely, only if you choose round and small numbers. 67% of 347 or 347% of 67 which one is easier?
347 is pretty damn close to 350.
350% of 67 =3.5 x 67 ~ 180+21+33=234
Within 1% is pretty good!
SPEAK ENGLISH! Jeez
I was waiting in a car in front of a math tutoring building and was doing the math problems advertised on their window (as one does, of course) and the 7% of 250 is indeed probably easiest as 250% of 7, aka 2.5x7, which is 17.5.
I did it a few other ways, though. 7% of 1000 is 70, then divide by 4 for 17.5. Well, more like, divide by 2 for 35 and again for 17.5, but yeah... mental math is fun.
👆 This guy.... fucks?
Calcufucks?
6% of 50
6/100 * 50/1
(6 * 50) / (100 * 1)
(50 * 6) / (100 * 1)
50/100 * 6/1
50% of 6
Works for multiplying any fraction, not just percents.
2/3 of 5 is the same as 5/3 of 2.
2/5 of 7/8 is the same as 7/5 of 2/8.
Yo what
So 50% of 50 is the same as 50% of 50. Both equal 5
Both equal 5
More like 5 of these
5 sweet dreams, got it
Who am I to disagree
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Multiplication is commutative.
50% of 6 == 50/100 x 6 == (50 x 6)/100 == 50 x 6/100 == 6% of 50.
True
taking x% is just multiplying by x/100, and multiplication is commutative. x% of y is just y×x×1/100, which is the same as x×y×1/100
you can also ignore the % and divide by 100 at the end. for example, what's 5% of 5? that might take a minute to work out. what's 25/100? you instantly know it's 1/4
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How is 17% of 83.27 easier then 83.27% of 17?
Oddly, yes.
Percentages also add together in partials. As in 10%+5%+2% = 17%
So, you start with the 10% by moving the decimal over 83.27 becomes 8.327
Then add half of that (5%) to its self and get 12.49 (rounded)
Then take the 10% number and move the decimal over once more (1%) for 0.833 and double it (from 1% to 2%) and get 1.666 and add that to your running total to get your answer of 14.16 (rounding)
And when I calculator check this I got 14.1559.
Great for calculating tips!
Let's see: the bill was $138.72, so I just need 138.72% of 20. And we can subtract 100% and just add the 20 back at the end, then convert the percentage to a decimal so (.3872 * 20) + 20 = 7.744 + 20 or $27.74.
Easy!
I prefer taking 10% and doubling it for a 20% tip.
Take the total, moved the decimal one digit to the left, double it and round to the nearest dollar. I round up at the beginning and end as well which is either close enough or a dollar high if the change is small enough.
$138.72 > 139 > 13.9 > 27.8 > $28
Close enough!
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(2 replies)
I always just do 10% (easy because you move the decimal one place) and then either double that or add half of it to itself for a 15-20% tip.
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I hate math so much.
Thank you for this
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