Amy can clean the house in 7 hours. When she works together with Tom, the job takes 4 hours. How long would it take Tom, working by himself, to clean the house?

A) $9 \frac{1}{3}$ hours

B) 3 hours

C) $10 \frac{1}{3}$ hours

D) $9 \frac{2}{3}$ hours

Question

Amy can clean the house in 7 hours. When she works together with Tom, the job takes 4 hours. How long would it take Tom, working by himself, to clean the house?

A) $9 \frac{1}{3}$ hours

B) 3 hours

C) $10 \frac{1}{3}$ hours

D) $9 \frac{2}{3}$ hours

Quizplus · Accepted Answer

Amy's rate is $1/7$ of the house per hour. Together, Amy and Tom's rate is $1/4$ of the house per hour. Subtracting Amy's rate from their combined rate gives Tom's rate as $1/4 - 1/7 = 3/28$ of the house per hour. Therefore, it takes Tom $28/3 = 9 \frac{1}{3}$ hours to clean the house by himself.

Amy Can Clean the House in 7 Hours 9139 \frac{1}{3}931​ Hours B) 3 Hours C)

Amy Can Clean the House in 7 Hours $9 \frac{1}{3}$ Hours

B) 3 Hours

C)