Working out percentages can often be people’s Achilles Heel but a revelation made on Reddit about how to work them out quickly has rattled many people to their core. Let us explain.
[referenced url=”https://www.lifehacker.com.au/2019/06/do-math-in-your-head-with-these-mental-math-tricks/” thumb=”https://i.kinja-img.com/gawker-media/image/upload/t_ku-large/bsyggwmhrdjhqvtg6g6g.jpg” title=”Quickly Do Maths In Your Head With These Mental Tricks” excerpt=”You probably haven’t had to do longhand maths in years, but you do mental maths every day. Or maybe you google maths problems ten times a day, because you’ve forgotten how to do any maths beyond your basic multiplication tables. Here are some shortcuts that will help you do more maths in your head.”]
Reddit user u/wlwlvr posted that an easy percentage hack meant you could reverse numbers to figure out the more simpler of the equations.
“Percentages are reversible. 8% of 25 is the same as 25% of 8 and one of them is much easier to do in your head,” u/wlwlvr wrote.
The thread was then filled with surprised users wondering how they’d never been told of such a simple maths hack.
How does it work?
Let’s break down how this mystical new knowledge actually works. Working out a percentage usually involves a fairly simple equation. For example, if you want to figure out 5 per cent of 60, you’ll need to break it down like this:
0.05 x 60 = 3
To do it in your head, if you’re like me, you’ll probably figure out what one per cent is and then multiply it by the percentage you want to find:
0.01 (1%) x 60 = 0.6, 0.6 x 5 = 3 so therefore the answer is 3
With u/wlwlvr’s trick, however, you would instead figure out the alternative equation and see if that’s any easier.
0.05 (5%) x 60 = 0.6 (60%) x 5
In this case, it’s not really any easier than the original equation but in some cases, it definitely will be. The example the user provided highlights that:
0.25 (25%) x 8 = 0.08 (8%) x 25 = 2
So it might not actually save your life every day, but it’s bound to help you in some situations. It’s not magic, it’s maths.
[referenced url=”https://www.lifehacker.com.au/2017/02/10-tips-to-improve-your-mental-maths-ability/” thumb=”https://i.kinja-img.com/gawker-media/image/upload/t_ku-large/hxso4qiinyksqtqjmmlm.png” title=”10 Tips To Improve Your Mental Maths Ability” excerpt=”Calculators are awesome, but they’re not always handy. More to the point, no one wants to be seen reaching for the calculator on their mobile phone when it’s time to figure out a 15 per cent gratuity. Here are ten tips to help you crunch numbers in your head.”]
This story has been updated since its original publication.
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