To solve this problem, let us say that the action of totally painting a small house is called “1 job”. Therefore the rates of each person in painting the small house are:
Bill = 1 job / 3 days = 1 / 3
Sharon = 1 job / 4 days = 1 / 4
Wilber = 1 job / 5 days = 1 / 5
Therefore the total rate is calculated by simply adding the rates of the three.
(1 / 3) + (1 / 4) + (1 / 5) = 1 / x
where x is the number of hours it take if all them paint together
Calculating for by multiplying both sides by 60:
60 [(1 / 3) + (1 / 4) + (1 / 5) = 1 / x]
(60/3) + (60/4) + (60/5) = 60 / x
20 + 15 + 12 = 60 / x
47 = 60 / x
x = 60 / 47 hours
Answer:
60/47 hours