Question

13 . A large tanker can be filled by two pipes a and b in 60 minutes and 40 minutes respectively. How many minutes will it take to fill the tanker from empty state if b is used for half the time and a and

Answer 1

let total time consumed in filling the tank is n.

(A+B)'s 1 minute work is 1/60 + 1/40 and (A+B) will take half of total time ie

(n/2)(1/60 + 1/40)----------(1)

and rest half will be filled by B only in half of total time means (n/2)(1/40)--(2)

(1)+(2)

(n/2)(1/60 + 1/40) + (n/2)(1/40)=1

n=30