Question

A b and c are 3 pipes attached to a cistern.A and b can fill in 20 & 30 minutes while c can empty it in 15 minutes.If a b c are kept open for 1 minute successively.How soon will the cistern be filled

Answer 1

I hope this answer is helpful for you....

Answer 2

Time taken by A alone to fill the tank= +20 minutes

in 1 min, work done by A = + 1/20

Time taken by B alone to fill the tank= +30 minutes

in 1 min, work done by B = + 1/30

Time taken by C alone to empty the tank= -15 minutes

in 1 min, work done by B = -1/15

=> work done by A,B,C combined in 1 minute= 1/20+1/30-1/15

=(3+2-4)/60=+1/60

=> Time taken to fill the tank by A,B,C= 60 minutes