RRB Paramedical Staff Nurse Model Paper 3

since,1st pipe takes 12 min to completely fill tank
Thus, tank filled by 1st pipe in 1 min =‌

1

12

Now, 2nd pipe takes 20 min to empty the full tank. Thus time taken by both pipes to fill complete tank
=‌

1

12

−‌

1

20

=‌

5−3

60

=‌

2

60

=‌

1

30

since, total tank will be filled in 30 min.
Hence, time taken to fill the half tank
=

30

2

=15 min