Question

If Al can paint a house in 15 hours and bill can paint the same house in 20 hours. How long will it take them if they work together?

Answer 1

See below.

Explanation:

Al can paint a house in 15 hours, which means in one hour, he can paint 1/15.

Using the same logic, bill can paint 1/20.

Together in one hour, they paint 1/15 + 1/20 = 7/60

Total hours: 60/7 = 8.57 hours. (8 hours and 34 minutes)