SAT Math Multiple Choice Practice Question 292: Answer and Explanation
6. Pump A, working alone, can fill a tank in 3 hours, and pump B can fill the same tank in 2 hours. If the tank is empty to start and pump A is switched on for one hour, after which pump B is also switched on and the two work together, how many minutes will pump B have been working by the time the tank is filled?
Correct Answer: A
A If pump A can fill the tank in 3 hours, then it will fill of the tank in 1 hour, leaving of the tank to fill. Pump B can fill ? of the tank in an hour, so working together, the two pumps can fill of the tank per hour. To fill of the tank working together, then, takes hour, which equals minutes.