Question

Two fill pipes can fill a cistern in 36 and 45 minutes respectively and one empty pipe can empty
the full cistern in 30 minutes. If the empty pipe is opened 7 minutes after both fill pipes are opened,
find when the cistern is full?​

Answer 1

Step-by-step explanation:

Part filled in 7 min =7×(

36

1

+

45

1

)=

20

7

Remaining part =1−

20

7

=

20

13

Net part filled in one minute when A, B and C are opened =

36

1

+

45

1

−

30

1

=

60

1

20

13

part is filled in 60×

20

13

=39 mins

Total time taken to fill the tank =(39+7)=46 min