Question

Using mental math, the approximate tip to leave for a bill of $81.79, if you tip 15% would be _____..

Answer 1

81.79 is approximately 80.
10% of 80 is 8
20% of 80 is 16
15% is right in between 10% and 20%, so the tip should be $12 which right in between $8 and $16.

Answer 2

About $12.30

($12.27)