A small pump can drain a pool in 7 hours. A large pump could drain the same pool in 3 hours. How long​ (to the nearest​ minute) will it take to drain the pool if both pumps are used​ simultaneously?

Answer 1

1/7 + 1/3 = 1/T

multiply by 21T

3T + 7T = 21

10T = 21

T = 21/10 = 2.1 hours with both pumps together = 2 hours and 6 minutes