15% is as easy as 20%

Ah, that’s just as easy.

$28.00 * 10% = 2.80

What’s 1/2 of 2.80?

1.40.

2.80 + 1.40 = 4.20

This works because 5% is 1/2 of 10%.

Or you could say they go down by the same ratio. There’s 10 10s in 100 and 20 5s in 100.

Or folding paper.  That’s how I like to do ratios in my head.  Anyway,  the decimal point trick works.

Leave a comment

Your email address will not be published. Required fields are marked *


six × = 36

Leave a Reply