Question

Two hoses from two different taps are used to fill a fishpond. The first hose alone

takes 20 minutes to fill the fishpond. The second hose alone takes 30 minutes to
fill the fishpond. How long would it take to fill the fishpond if both hoses are used?

Answer 1

Answer: 12 minutes

Explanation:

Two rates for hoses A and B. FP is the Fish Pond.

A = 20 min/FP or (1/20)FP/min

B = 30 min/FP or (1/30)FP/min

The time in minutes, X, to fill one FP:

1FP = X*((1/20)FP/min) + X*((1/30)FP/min)

1FP = X*(1/20+1/30)FP/min

1FP = X*(2.5/30)FP/min

X = 12 minutes