Question

A brother and a sister are assigned to clean up their family house. The sister cleans the house in 7 hours working alone. The brother can do the same work in 5 hours. How long does it take them to clean up together

Answer 1

Explanation:

Rate1 = 1 house / 7hr

Rate2 = 1 house/ 5hr

Now find the time required when both rates are combined

1 house / ( 1/7 + 1/5) = 2 11/12 hr = 2.92 hr