Gus works three times as fast as Sid. Together they can dig a garden in 3 hr. How long would it take each person working alone?
Let's assume that Sid can dig the garden in x hours. Since Gus works three times as fast as Sid, he can dig the garden in x/3 hours.
Working together, their combined work rate is 1/x + 1/(x/3) = 1/3.
Multiplying through by 3x, we get 3 + x = x. Simplifying, we get 3 = 2x, so x = 3/2 = 1.5 hours for Sid to dig the garden on his own, and 1.5/3 = 0.5 hours for Gus to dig the garden on his own.