Two pipes fill a pool. Pipe A fills it in 4 hours, Pipe B in 6 hours. If both work together, how long does it take?
Answer
2.4 hours
How to solve it
1
Pipe A rate: 1/4 pool per hour
2
Pipe B rate: 1/6 pool per hour
3
Combined rate: 1/4 + 1/6 = 3/12 + 2/12 = 5/12
4
Time: 1 ÷ (5/12) = 12/5 = 2.4 hours
Hints
Find each pipe's rate (fraction per hour)
Add the rates together
Take reciprocal to find time