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

Seriously, why didn't anyone?! Would have made my life much easier.

So, is 289.8 the magic, double "nice" number?

Weed and Adderall sound like a dope ass combo.

29% of 29 is 29% of 29

Fuck, this trick sucks.

33% is the easy one.... 1/3 of 6 is 2, 1/3 of 1 is 0.33... 2.33..

1% of 33 is .33

.33 × 7 =

.3 x 7 = 2.1

.03 x 7 = .21

21 + 2.1 = 2.31

So

7% of 33 = 2.31

You could also do

33% of 7

10% of 7 is .7

1% of 7 is .07

So 11% is .77

.77 × 3 =

.7 × 3 = 2.1

.07 × 3 = .21

2.1 + .21 = 2.31

x% × y = x × y ÷ 100 This helps you out much more.

Well, single digit percentages are easy. If it helps, move your decimal to the right so 9% becomes 90%. You can probably calculate 90% of 3 because you can do 10% and subtract it and get 2.7. Now move your decimal back to the left and you get 9% of 3 which is 0.27. You can do the same with higher percentages once you learn to break them in to 10% pieces.

You're really asking whether commutativity of multiplication has ever helped anyone? Because that's what this is.

And yes it has helped me eg. estimate things or whatever along the years – but of course it's not going to be some sort of magical mathematics trick where just by reversing the numbers it'll always make things easier to calculate in your head

I'd find 9% of 3 easier for sure. Sometimes it's easier sometimes it's not. Just use it when it's easier.

Wait are you questioning the wisdom of panzer of the lake?!

This tip helped me 21%

You can work it out yourself. 6% is the same as 6/100, so 6% of 50 is (6/100)*50. Then do some algebra and see if you can jiggle it to say (50/100)*6. Then replace 6 and 50 with Greek letters so it looks more convincing.

Why would I do that

Instructions unclear...

09, 108, 1107, 11106, 111105

You can multiply by 9 on your fingers.

Hold hands out, fingers splayed, thumbs towards each other. 🙌

9*2 put your left ring finger down (the 2nd finger). Left of that is tens place, right of that is the ones place.

So 1 on the left, 8 on the right of the downed finger.

9*5 put the left thumb down (5th finger.) 4, 5. 45.