A box has 900 balls. 90% are red.

see how different people might think about it.

Ready?

First, let’s use normal everyday logic.

If 90% of the balls are red, that means 10% are not red.

So we only need to find 10% of 900.

A simple way is to divide 900 by 10.

900 ÷ 10 = 90.

So the usual answer is:

90 balls are not red.

Easy, right?

We can also check it another way.

If 90% are red, then:

900 × 0.continue reading …