An inlet pipe can fill an empty swimming pool in 7 hours, and another inlet pipe can fill the pool in 2 hours. How long will it take both pipes to fill the pool?

1.56 hours

Step-by-step explanation:

Given,

Rate of first inlet

= 1 pool per 7 hours

= (1/7) pool per hour

Rate of 2nd inlet

= 1 pool in 2 hours

= (1/2) pool per hour

Combined rate = Rate of 1st inlet + Rate of 2nd inlet

= 1/7 + 1/2

= 2/14 + 7/14

= 9/14 pool per hour

taking the inverse of the combined rate gives the time it takes to fill the pool in hours. Hence,

Time for Both pipes to fill the pool = 1 / (9/14) = 14/9 = 1.56 hours