Question

a painter can finish a house in 5 hours. Her assistant takes 7 hours to finish the same job. How long would it take for them to complete the job if they were working together?

Answer 1

D

Explanation:

Call the first person A who can do the job in 5 hours.

Call the second person B who can do the job in 7 hours.

The formula for this problem is

Time = A*B/(A + B)

Time = 5*7 / (5 + 7)

Time = 35 / 12

Time = 2 hours and 11/12 of an hour.

The answer is D.