Question

The sales tax in Kadisha's state is 5%. Kadisha says she computes 15% tip by multiplying the tax shown on her bill by 3. For a bill with a tax charge of $0.38, Kadisha's tip is $0.38 x 3 = $1.14. Why does Kadisha's method work?

Use the same method to compute a 20% tip.

Answer 1

"Kadisha's method works because 15% is 3 times 5%, and both amounts are computed on the amount of the bill before tax is added."