Maths hacks: Video playlist

Calculating percentages is something you should be confident about.

Here’s a couple of hacks to make them easier and faster to solve.

Firstly, when asked to find the percentage of a number, here’s a handy trick for you.

Swap the numbers around.

So, what’s 14% of 50?

It’s tricky, right?

But if you swap the numbers to work out 50% of 14, this will give you the same answer.

50% of 14 is 7, and 14% of 50 is also 7.

Pretty cool right?

It’s all because x% of y gives you the exact same answer as y% of x.

And this method will work with any percentage conversion.

12% of 75?

Swap it round to 75% of 12 and now you need to find 3 quarters of 12, which is 9, and 9 is also 12% of 75.

Okay here’s another hack that’s very useful when increasing or decreasing the value by a percentage.

It’s called the decimal multiplier hack.

Every percentage has an equivalent decimal value.

If your favourite shop sends you an email offering you a 20% discount, you can use this hack to work out the new price of an item you want.

To decrease something by 20%, you multiply by the decimal equivalent of 80% because 80% is 20% less than the original amount, 100%.

80% as a decimal is 80 divided by 100, which equals 0.8.

Let’s say that £40 top you’ve got your eye on, is reduced by 20%.

You have to multiply 40 by 80% as a decimal, which is 0.8.

40 times 0.8 equals £32.

And to increase by a percentage is similar.

For example, train tickets often go up in price during peak travel times.

If you wanted to increase a value by 30%, you need to multiply by the decimal equivalent of 130%, as this is 30% more than the original amount - 100%.

130% as a decimal is 130 divided by 100, which equals 1.3.

So, if we want to increase 80 by 30%, you have to multiply 80 by 1.3, which equals 104.