Problema Solution
A community water tank can be filled in 18 hours by the town office well alone in 22 hours by the high school. How long will it take to fill the tank if both wells are working?
Answer provided by our tutors
Time taken by town office well to fill the tank = 18 hrs.
So quantity filled in 1 hr = 1/18 th part of the tank
Time taken by high school well to fill the tank = 22 hrs.
So quantity filled in 1 hr = 1/22 nd part of the tank
When both the wells are open, quantity filled up in 1 hr =1/18 + 1/22
= (11+9)/198 [taking LCD]
= 20/198 part of the tank
So time needed by both the wells to fill the tank = 198/20 hrs
= 9.9 hrs
= 9 hrs 54 min