October 2012
Problem of the Month

Tipping Problem

On the last night of the family trip to San Diego, Mr. P paid for dinner for all 14 family members.   The bill was $197.54 but it already included an 18.25% gratuity.   Mr. P always tips 20% but he didn't have time to do the math, so he just added two dollars to make the total $199.54.

What percent did Mr. P actually tip?

Solution to the Problem:

The answer is 19.45%.

Let x = amount of the food before any tip is added.
Then x + .1825x = 197.54
So, x = 167.05 (the cost of the food)
So, the 18.25% tip was $30.49
Since Mr. P added 2 dollars to the tip,
the actual tip that he left was $32.49
So, Mr. P left a 19.45% tip (32.49 / 167.05)

Correctly solved by:

1. James Alarie	Flint, Michigan
2. Kyla Hoopes	Mountain View High School, Mountain View, Wyoming
3. Larissa Giessinger	Mountain View High School, Mountain View, Wyoming
4. Chad Fore	Gate City, Virginia

Send any comments or questions to: David Pleacher