Question

Tap A can fill a cistern in 12 hours and Tap B can empty the cistern in 18 hours . How much time it will take to empty the cistern if both the taps are opened together ?​

Answer 1

$\huge\mathtt\pink{A}\mathtt\red{N}\mathtt\blue{S}\mathtt\green{W}\mathtt\purple{E}\mathtt\green{R}$

Given:-

• pipe a can fill cistern in 18hours
• pipe b can fill cistern in 12hours

To find:-

• how much te both will take to fill cistern if opened together

Solution:-

a's 1 hour work= 1/12

b's 1 hour work= 1/18

there 1 hour work if opened together= 1/12 + 1/18

$\large \: \frac{1}{12} + \frac{1}{18} = \frac{3 + 2}{36}$

$\large \rightarrow \: \frac{5}{36}$

Now they will fill cistern in

$\large \rightarrow \: \frac{36}{5} = 7hours \: 12minutes$