This simple math trick generated tweet-storm

The trick has went viral on Twitter and has been described as a "fascinating little life hack".

(Web Desk) – Sometimes it becomes troublesome to calculate percentages within short time frame and without using calculators, particularly during exams, but a simple trick of mathematics can make it incredibly easy to perform unwieldy calculations on the spot.

The trick has went viral on Twitter and has been described as a "fascinating little life hack" by UK-based copywriter Ben Stephens.

It involves only swapping the number to figure out an answer. It is not a new technique, but the huge reaction online shows a lot of people never knew that it existed.

As Stephens explains, if you ever have to calculate a difficult percentage on the spot without pen and paper or a calculator, you can use a simple shortcut - flip the numbers around.

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

Indeed, if you swap the numbers and calculate 75 percent of 4, you get 3 – and 3 is the same answer when you calculate 4 percent of 75. (In case it doesn’t click straight away, 75 percent is three quarters, so in this case it becomes a simple division problem.)

Another example: "18% of 50 appear hard to calculate," Stephens wrote. "But 50% of 18 is a doddle, right?"

The basic principle is – simply stated as x% of y = y% of x – probably well known to millions of people across the world.

But as the tweet-storm generated by Stephens’ original comment shows, it’s a mind-blowing discovery for many who were never made aware of this simple substitution, with one user saying the revelation "got me excited about math for the first time in decades."

Others said they knew about this ‘trick’ all along, having been taught it in school.

As some people point out, though, the technique doesn’t always necessarily work (in terms of making things simpler, at least).

For example, using the substitution with some calculations, like trying to calculate 17% of 12, would just give you 12% of 17 (which really isn’t any easier to do in your head).

Moreover, it a number gets larger or includes decimal (or other complications), it would not make percentages easier to calculate.

But as long as you’re dealing with fairly small numbers, it’s a real help.

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

I m really quite cross that this was NEVER taught in my maths class.

— mellymelmelmel (@pikminlover) March 7, 2019

how am I today years old to learn this. All the useless math taught at school & discovered this 30 years after leaving!!

— Robin Hartley (@RobinHartley2) March 8, 2019

Absolutely stealing this for my next science lesson!

I wish I d seen this thread when I was about ten years old.

— Roger O Keeffe (@rogerokeeffe) March 5, 2019

This is one of those weird things where, now that you ve pointed it out, it s so obvious that I wonder why I never knew it before.

— Safwan (@zinjabil) March 6, 2019

This is so cool... have a-level in maths and been coding for over 20 years... this will be so useful... don’t be deterred by people dissing it!

— James Stone (@mimeartist) March 6, 2019

Whoa...I teach Maths at primary level and had never realised this. 50% blown away/50% going DOH! pic.twitter.com/4yhxgFSgDq

— Magical Maths Notts (@MathsNotts) March 6, 2019

Really, is this new? I always thought that s the way to do it since being taught that in primary school in India 35 years ago. That s the only way I ve known. And I thought the whole world knew it.

— Nindy (@Happy_Andy) March 7, 2019

How could maths teachers let us live without this!

— Lom Harshni Chauhan (@lomharshni) March 5, 2019