Question

To collect data on the signal strengths in a neighborhood, Briana must drive from house to house and take readings. She has a graduate student, Henry, to assist her. Briana figures it would take her 12 hours to complete the task working alone, and that it would take Henry 18 hours if he completed the task by himself. How long will it take Briana and Henry to complete the task together?

a. 6.7 hours
b. 7.2 hours
c. 5.6 hours

Answer 1

The correct answer is B. It will take them 7.2 hours.

Explanation:

Given that to collect data on the signal strengths in a neighborhood, Briana must drive from house to house and take readings, and she has a graduate student, Henry, to assist her, and Briana figures it would take her 12 hours to complete the task working alone, and that it would take Henry 18 hours if he completed the task by himself, to determine how long will it take Briana and Henry to complete the task together the following calculation must be performed:

1/12 + 1/18 = X

18 / (12 x 18) + 12 / (18 x 12) = X

30/216 = X

5/36 = X

36/5 = 7.2

Therefore, they will be able to finish the task in 7.2 hours.