Question

There are 2 inlet a and b take 20 hrs to fill tank tape a alone kept 15 hrs and closed remaining b will do in 21 hrs how much time a alone fill

Answer 1

Answer:

a=120 hrs

Step-by-step explanation:

a and b take 20 hrs.  From here (1/a)+(1/b)=1/20

a alone 15 hrs + b alone 21 hrs. From here (15/a)+(21/b)=20/20

Let's multiply the first equation by 21 in order to get rid of term with b in the second equation..  (21/a)+(21/b)=21/20. Subtract the second equation

                                (15/a) +(21/b)=20/20

     6/a=1/20 ⇒a=120