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 find how long it will take for both pumps to fill the tank together, we can determine the combined rate at which they fill the tank.
The first pump fills 1/4 of the tank in 1 hour, which means it has a rate of 1/4 tank per hour.
The second pump fills 1/3 of the tank in 1 hour, which means it has a rate of 1/3 tank per hour.
When both pumps are used at the same time, their rates are added together:
1/4 + 1/3 = 3/12 + 4/12 = 7/12 tank per hour
Therefore, the combined rate at which the pumps fill the tank is 7/12 tank per hour.
To find out how long it will take both pumps to fill the tank, we take the reciprocal of the combined rate:
12/7 ≈ 1.7 hours
Therefore, the answer is B) about 1.7 hours.