Question

One pipe can fill a tank in 24 minutes, a second can fill it in 8 minutes, and a third can fill it in 12 minutes. If the tank is empty, how long will the three pipes, operating together, take to fill it?. . A. 1/6 minute.B. 4 minutes. C. 4 4/5 minutes

Answer 1

the answer is option b that is 4 minutes .
we can solve it by this formula
1/24 + 1/8 + 1/12 = 1/x 1/24 + 3/24 + 2/24 = 1/x 6/24 = 1/x x(1/4) = 1 x = 4

Answer 2

Total volume of the tank = V

Rate of the first pipe = V / 24
Rate of the second pipe = V / 8
Rate of the third pipe = V / 12

If all of them operates at the same time, time taken is t.
V = (V/24 + V/8 + V/12) t
V = (V + 3V + 2V)/24 * t
V = 6V/24 * t
t = 24/6
t = 4 minutes

So the answer is B