Twitter user Ben Stephens recently “[set] the internet on fire” after tweeting one “fascinating little life hack” for percentages that the internet has since deemed “life-changing”.

Ben explained that if kids are struggling to work out a percentage of a number, they can swap the two numbers around to make things easier because the answer will still be the same.

“For example, if you needed to work out 4% of 75 in your head,” he says, “Just flip it and do 75% of 4, which is easier.” 

And it’s true – the answer is 1 both ways.

24% of 50 = 50% of 24 = 12

20% of 75 = 75% of 20 = 15

15% of 20 = 20% of 15 = 3