Question

A tank can be filled by one tap in 20 min and by another in 25 min. both the taps are kept open for 5 min and then the second tap is turned off. in how much more time will the tank be filled?

Answer 1

Solution

Work done by both in 5 minute = (1/20 + 1/25) = 9/20
Remaining part = (1 - 9/20) = 11/20
Now, 1/20 part is filled in 1 minute. So, 11/20 part will be filled in 11 minute.
Hence, the tank will be full in 11 min more

Answer 2

Answer:

The time taken by one tank is 11 minutes to be filled.

Step-by-step explanation:

Given : A tank can be filled by one tap in 20 min and by another in 25 min. both the taps are kept open for 5 min and then the second tap is turned off.

To find : In how much more time will the tank be filled?

Solution :

A tank can be filled by one tap in 20 min

Work done in 1 min is $\frac{1}{20}$

A tank can be filled by other tap in 25 min

Work done in 1 min is $\frac{1}{25}$

In 5 minutes work done by both pipes is

$\frac{5}{20}+\frac{5}{25}=\frac{9}{20}$

After 5 min second tap is closed,

So first tap has to work to complete the work

Now, Remaining work done is

$1-\frac{9}{20} =\frac{11}{20}$

Which means the time taken by one tank is 11 minutes to be filled.