Question

A lunch bill was $19.50. Mark wants to leave a 20% tip but does not want to wait for change. Which of the following is a reasonable estimation of how much Mark should leave?

a.)$30

b.)$18

c.)$21.50

d.)$24

Answer 1

d $24 is the answer as 20% of 19.50 is 3.9 hence the total amount becomes 19.50 + 3.9 = 23.4....the closest is $24

Answer 2

The way I'd approach a problem such as this is to look at what kind of tip would be exactly 20%. You want to leave 20% of the total (or 100%) of the bill. The shortest way to do this would be to take 19.5 and multiply it by 1.2. This gives you %120 of your bill (100% of the bill, and a 20% tip). That value is $23.40. Compare that value with the answers above, and you'll see it's closest to $24.