WTF why did no one mention this to me when I was struggling with math as a kid?
They probably did, just not explicitly:
You could write (6*1/100)*50 = 6*(50*1/100)
It only uses the commutative property of multiplication and the fact that % is another way of writing 1/100.
Maybe also worth remembering that “x% of y” is just x/100*y
The word percent is exactly that per cent, which basically means parts of hundred. E.g. 10% are 10 of 100, or 60% are 60 of 100. You can also write this mathematically as 60/100 or 60÷100, which is 0.6.
Now in general: x% are x parts of 100 or x/100 or x÷100. If you want to calculate x% of y you just multiply it: y × x% = y × x ÷ 100.
I totally remember being taught this. It’s just way easier to break down percentages in terms of the nearest 1% or 10% times the number in the percent times the number you’re taking the percentage of. You don’t have to do the math for the 1 or 10 percentage as long as you remember that a 10% means move the decimal left once and 1% means move the decimal left twice. The rest is just basic multiplication.
40% of 59 = 10% of 59 times 4.
So…
4x59=236
or
(4x50=200) + (4x9=36)= 236
10% means move the decimal left once,
Therefore 40% of 59 is 23.6
With that you can easily do more complex percentages mentally like…
62% of 35 = 10% of 35 times 6 plus 1% of 35 times 2.
35x6=180+30=210 at 10% so 21
plus
35x2=60+10=70 at 1% so 0.7
Therefore 62% of 35 = 21.7
While I get your sentiment, I’m always baffled how people fail to just memorize some basic formulas/equations and then just to plug and play:
1÷kⁿ = k⁻ⁿ
% = 1÷100 = 10⁻²
k×10ⁿ equals k with its floating point shifted by n to the right for positive n, or to the left for negative n
That’s really all one needs to know for the “problem” at hand. For your concrete example of “40% of 59” that would just be
59×40×10⁻²
Just solve that whatever way is easiest. I don’t get why people get panic-stricken when they see the % sign.
they absolutely taught you the commutative property and transitive property
Easy way to do %
Say you want 6% of 45
Seems hard right?
1% of 45 is .45
.45 × 6 =
.4 × 6 = 2.4
.05 × 6 = .3
2.4 + .3 = 2.7
So 6% of 45 is 2.7
Extra:
Say you want an item that is 40 dollars and it is 20% off.
10% is 4 dollars.
20% is 8 dollars.
So item would be 32 dollars.
that’s a shitload of lines of math to write out/work in your head. I learned percentages of x as: 6 * 45 / 100 = x (2.7) If you picture both as fractions, you multiply the opposite and then divide by the other number to get the missing one (x). Hopefully Lemmy renders this well…
| 6 | x |
| 100 | 45 |
The way I learned it was multiply diagonally and then divide by whatever is opposite diagonally to x.
… because multiplication is commutative.
69% of 420 is equal to 420% of 69.
Bro that’s actually amazing
Idk if it’s the weed, the adderall, or the ADHD, but this thread is everything I need in my life.
Honestly I recently switched to vyvanse and I don’t actually smoke to get high (at least not until the kids are in bed). I just microdose a bit throughout the day and it balances out the vyvanse. Like, the stimulants alone are just a little bit too much for me. The combo, though, I can dial in just right.
But weed alone always made me fixate on arithmetics. And then stims turn that up to 11.
