The swimming pool can be filled in 40 hours using the medium hose. With the large hose, it will take \(20\) hours instead. If we use both hoses (without any impact on waterflow rate), how long does it take to fill the pool? Round your answer to the nearest hour.
+2668 The medium hose can fill 2.5% of the pool in an hour.
The large hose can fill 5% of the pool in an hour.
Both together can fill 7.5% of the pool in an hour.
This means it will take \(100/7.5 \approx \color{brown}\boxed{13}\) hours.
+37146 Rate 1 = 1 pool /40 hours rate 2 = 1 pool / 20 hours
now
1 pool / combined rate = ? hours
1 / ( 1/40 + 1/20) = 1 / ( 3/40) = 40 / 3 hours = 13 hours 20 min ~~ 13 hours
