Question

a cistern can be filled by one tap in 12 hour and by another in 15 hour how long will it take to fill the cistern if both tap are opened together​

Answer 1

Answer:

20/3 hrs

Step-by-step explanation:

one tap fills it in 12hrs

1hr work done by tap 1 = 1/12

second tap fills it in 15hrs

1hr work done by tap 2 = 1/15

now both taps are open

1hr work done = 1/12 + 1/15

1+2 = (15+12)/180 = 27/180 = 3/20

Inverse of above give us the time to fill cistern fully

= 20/3hrs = 6.2/3 hrs