Question

Tap A fills a tank in 3 hours, outlet pipes B and C can empty the tank in 4 hours and 6 hours respectively. If the
tank is empty and taps A and Bare turned on, then how long will it take to fill up? After the tank is full, taps A
and C' are all turned on. How long will the tank take to be emptied?

Answer 1

Answer:

Step-by-step explanation:

Answer 2

Answer:

Tap A fills a tank in 3 hours

Tap A's 1 hour work = $\frac{1}{3}$

Tap B can empty the tank in 4 hours

Tap B's 1 hour work = $\frac{1}{4}$

Tap (A+B)'s 1 hour work = $\frac{1}{3}-\frac{1}{4}=\frac{1}{12}$

So, the tank will be full in 12 hours

C can empty the tank in 6 hours .

C's 1 hour work = $\frac{1}{6}$

Tap (A+B+C)'s 1 hour work = $\frac{1}{3}-\frac{1}{4}-\frac{1}{6}=-\frac{1}{12}$

So, it will take 12 hours to be emptied