Question

A kiddie pool holds 161 gallons of water. One hose can fill the pool in 3 hours while an-
other takes only 2 hours. How long will it take for the pool to be filled if both hoses are
used?

Answer 1

The first hose pumps out water at a rate of

(161 gal)/(3 h) = 161/3 gal/h

The second hose fills the pool at a rate of

(161 gal)/(2 h) = 161/2 gal/h

Working together, they can fill the pool at a rate of

(161/3 + 161/2) gal/h = 805/6 gal/h

so that it would take

(161 gal) / (805/6 gal/h) = 161×6/805 h = 6/5 h = 1.2 h = 1 h 12 min

to fill the pool.