 one an incredible maths hack, here's one. So, if you're trying to work out 7% of 50, you might be thinking, how do I do that? Actually, you can. Flip it round. Make it 50% of 7, which you can do, and that's three and a half. And why does this work? And it's because x percentage of y is the same as y percentage of x. And that's because multiplication is commutative, and that's where 4 times 7 is the same as 7 times 4. The order doesn't matter. Let's try one more example. So, how about working out 40% of 75? Looks tricky, but let's do a method. Flip it round. 75% of 40, that is 30. And there you go. That's a fabulous maths hack.