# Viral Maths Trick Has Everybody Asking Why It Wasn’t Taught In School

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Admittedly maths isn’t one of my strong points, leaving me reaching for the calculator app on my phone for even the most basic sums.

Despite my A* in GCSE Maths (go 15-year-old me), I seem to have forgotten everything I learnt at school thanks to my awful memory.

Luckily I don’t need to use maths that often, but if I do it is often percentages, which can be difficult.

If you wanted me to work out a percentage, I would just divide the number by 100, before multiplying to get the result.

For example, to get 18 per cent of 50, I would divide 50 by 100, then multiply that number by 18 to reach the answer, which is 9.

However, there is a quicker way to work this out, as ‘maths whizz’ Ben Stephens explained on Twitter.

In a tweet Ben pointed out all you have to do is switch the sum around and the maths becomes much easier.

He explained:

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.

The answer of course is 3 for both sums, but the latter is much simpler.

It is no wonder then the tweet has received over 18,000 likes at time of writing (March 12).

People were surprised they were never taught this in school, thanking Ben for the hack.

Sandhya Ramesh wrote:

This sounds like something everyone should ideally have known in high school but I’m today years old when I realized I can’t think in even basic math.

GGGAAAHHHHHHHHH EVERY TEACHER I EVER HAS FAILED ME, AND I DON’T MEAN MY GRADES

Nick Harvey tweeted:

The whole world needs to know this.

A maths teacher appreciated the tip tweeting:

Whoa…I teach Maths at primary level and had never realised this.
50% blown away/50% going DOH!

Kamal agreed writing:

Have a degree in Applied Mathematics and never knew that.

Of course the trick only works for certain sums, especially if the numbers are round like 50, 25 or 75.

For example, if you want to work out what 43 per cent of 87 is, trying to calculate what 87 per cent of 43 is is just as difficult.

However, it is handy to know and could be useful!

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