One pump can fill a tank with oil in 4 hours. A second pump can fill the same tank in 3 hours. If both pumps are used at the same time, about how long will they take to fill the tank? Round to the nearest tenth. a. About 2.1 hours b. About 1.7 hours c. About 7 hours d. About 3.5 hours
To figure out how long it will take both pumps working together to fill the tank, we need to find the combined rate at which they fill the tank.
The first pump fills the tank in 4 hours, so its rate is 1/4 tanks per hour.
The second pump fills the tank in 3 hours, so its rate is 1/3 tanks per hour.
When both pumps are working together, their rates are additive:
1/4 + 1/3 = 7/12
Therefore, both pumps together can fill 7/12 of the tank in one hour. To find the time it takes to fill the whole tank, we take the reciprocal:
12/7 ≈ 1.7 hours
Therefore, the answer is b. About 1.7 hours.