Question

Pump A alone can empty the city pool in 12 hours. If only pump B is used, it takes 24 hours to empty the pool. How long would it take to drain the pool if both pumps were used together?

Answer 1

A 1/12 pool / hr
B 1/24 pool / hr

together 3/24 pool/hr

so 24/3 = 8 hr/pool