A simple mathematical life hacking, how quickly calculate the percentage of the number of

Quickly calculate the percentage of a number without a calculator is not so easy. Even if you have a good divide and multiply in your mind, you are unlikely to find quickly, for example, 4% of the 75. If we know a mathematical trick, the answer can be obtained instantly.

Everything is extremely simple: x% by y = y% of x. In other words, 4% of 75 = 75% of 4. In this example, 75% of 4 much easier to find - it is 3. If you check the first part, you get the same thing: 75/100*4 = 3.

Fascinating little life hack, for doing percentages:

x% of y = y% of x

So, for example, if you needed to work out 4% of 75 in your head, just flip it and and do 75% of 4, which is easier.

- Ben Stephens (@stephens_ben) March 3, 2019

This uncomplicated rule on Twitter reminded Ben Stephens. And judging by the 6000 retweets and 17,000 likes, many users have no idea about such tricks. However, it is worth noting that it is possible to use not always. There are "inconvenient" figure where this trick will not work. For example, 21% of 27, or 19% of 89.

And did you know these tricks, which are known not for everyone? Share in the comments.