SOLUTION: (Time required to do a job) Two pumps are available for filling a gasoline storage tank. Pump A, used alone, can fill the tank in 3 hours, and pump B, used alone, can fill it in 4

Algebra ->  Rate-of-work-word-problems -> SOLUTION: (Time required to do a job) Two pumps are available for filling a gasoline storage tank. Pump A, used alone, can fill the tank in 3 hours, and pump B, used alone, can fill it in 4      Log On


   



Question 781310: (Time required to do a job) Two pumps are available for filling a gasoline storage tank. Pump A, used alone, can fill the tank in 3 hours, and pump B, used alone, can fill it in 4 hours. If both pumps are used simultaneously, how long will it take to fill the tank?
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
The sum of their rates is the filling rate when both pumps work at the same time.
Pump A, 1/3 tanks per hour
Pump B, 1/4 tanks per hour

Pump A and B Together, %281%2F3%29%2B%281%2F4%29 tanks per hour
4%2F12%2B3%2F12
7%2F12 tanks per hour.

The other way to describe this combined rate is 12%2F7=highlight%281%265%2F7%29 HOURS to fill THE TANK.