Tap A fills a tank in 4hours while B fills the same tank in 3hours. Tap C empties this tank when full in 2hours. If the tank is initially empty and all three taps are opened, how long will it take to fill the tank?

It will take 12 hours to fill the tank

Step-by-step explanation:

Proportions

Tap A fills a tank in 4 hours. It means each hour it fills 1/4 of the tank.

Tap B fills the tank in 3 hours. Each hour it fills 1/3 of the tank.

Tap C empties the tank when full in 2 hours. Each hour it empties 1/2 of the tank.

Each hour, the tank gets filled by:

Since the tank fills 1/12 of its capacity in one hour, it follows that it will take 12 hours to fill the tank

21

step-by-step explanation: