Question

A tap fills a tank in 4 hours. Another tap empties the full tank in 6 hours. How long will it take to fill the tank,if the tank is empty and both the taps are open

Answer 1

Part of the tank filled in 1 hour = 1/4
Part of the cistern emptied in 1 hour = 1/6
When both the taps are opened simultaneously, part of cistern fill in 1 hour = 
$\frac{1}{4} - \frac{1}{6 } \\ \frac{3 - 2}{12} \\ = \frac{1}{12}$

Hence, the cisatern wil be filled in 12 hours.

(reversed 1/12 since it is a time )


hope it helps to you.

Answer 2

Answer:

12 hours

Step-by-step explanation:

A tap fills a tank in 4 hours.

Tap 1 hour work = $\frac{1}{4}$

Another tap empties the full tank in 6 hours.

Tap 1 hour work =$\frac{1}{6}$

Their together 1 hour work = $\frac{1}{4}-\frac{1}{6}=\frac{1}{12}$

So, They together fill the tank in 12 hours

Hence if the tank is empty and both the taps are open then it will take 12 hours to fill tank