Math Word Problems Demystified - A Self Teaching Guide

The LCD is 15.

153

1



x

51

þ

155

1



x

31

¼ 15  1

3 xþ 5 x¼ 15

8 x¼ 15

x¼

15

8

or 1:875 hours

Hence, if both pipes are turned on at the same time, it would take

1.875 hours.

EVALUATION: Check the equation:

x

5

þ

x

3

¼ 1

1 : 875

5

þ

1 : 875

3

¼ 1

0 : 375 þ 0 : 625 ¼ 1

1 ¼ 1

As you can see, both types of problems can be done using the same

strategy. The next examples show some variations of work problems.

EXAMPLE:A person can clean a small office building in 8 hours and her

assistant can clean the same building in 12 hours. If, on a certain day, the

assistant shows up two hours late and starts to work, how long will it take

both people to clean the building?

SOLUTION:

GOAL: You are being asked to find the time it takes both workers to clean

the building.

STRATEGY: Letx¼the time it takes to clean the rest of the building when

both people are working.

184 LESSON 17 Solving Work Problems