Question

20% tip on a bill of 31.60

Answer 1

6.32

Explanation:

There's an easy trick for this. Move the decimal point once to the left, and then multiply by 2.

31.60 turns into 3.16 (which is 10% btw)

Multiply 3.16 by 2 and you get 6.32, or 20% of 31.60. Hope this helped!