Title: Lesson 8-4
Author: Unknown User
Last saved by: The McGraw-Hill Companies
Company: DellComputerCorporation

Lesson 7-5 Problem-Solving Investigation

Determine Reasonable Answers

DINING  Mr. and Mrs. Hawthorne have just completed a meal at a local restaurant.  The cost of the meal is $51.78.  How much money should they leave as a tip if they want to give the server a tip that is approximately 15%?

UNDERSTAND | The total cost of the meal is $51.78.  The Hawthornes want to leave a 15% tip.
PLAN | Round $51.78 to $50.  Then use mental math to find 15% of 50.

SOLVE

Round $51.78 to $50.
10% of 50 = 0.1  50 or 5
5% of 50 = 0.5  5 or 2.5
15% of 50 = (10% of 50) + (5% of 50)
                 = 5 + 2.5 or 7.5
So, $7.50 would be an appropriate tip.

CHECK

Use a calculator to check.
0.15    51.78  ENTER  7.767.  So, the answer 7.5 is reasonable.