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.
