# This Viral Math Hack is Making Even Math Teachers Ask ‘How Did I Not Know This?!’

It’s fair to say that for a lot of folks out there, math class was a serious struggle throughout most of school. (It was pretty much a losing battle after multiplication tables for this writer).

A recent tweet is blowing not just the minds of the math handicapped but legitimate math teachers as well. This may just be the only time that the internet has been excited over a math lifehack, so pay attention.

Percentages are one of those things that so many people struggle to figure out in their head — hence the reason every phone has a calculator. It’s probably safe to assume that 90 percent of society would be either horrendously undertipping or gloriously overtipping at restaurants without them.

Say you wanted to calculate 4 percent of 75. Without using a calculator this would very possibly send a lot of us into a mental sweat.

Math smartypants Ben Stephens, tweeted out a very simple trick. To borrow from Missy Elliot, simply “flip it and reverse it.”

## The internet demanded to know why they didn’t learn this math hack in school.

Using this approach it’s pretty obvious that the answer is three. It’s not crazy easy 100 percent of the time, but it certainly comes in handy quite a bit as Stephens demonstrated a few more examples.

“18% of 50 feels hard to calculate,” he wrote, and he is right it does at first glance. “But 50% of 18 is a doddle, right?”

Raise your hand if you shouted out “It’s 9!” Don’t you feel a little bit like a math genius and suddenly very disappointed in every math teacher you’ve ever had and the American education system at large?

This guy might want to have a few words with his English teacher as well.