Three pipes A,B and C working together can fill a cistern in 6 hours. After working together for 2 hours, C is closed and A&B fill it in 7 hours more. How many hours will C alone take to fill the cistern?

Ans.14
Let work = 42 units and solve.

Let total work = 6(A+B+C)
Also, ATQ, TW = 2(A+B+C) + 7(A+B)
Equating, we get,
C = 3(A+B)/4
Substitute this value in the expression -
= [6(A+B+C)]/C
Solve by separating A & B, everything will get cancelled and you'll get 14 hours
Solved under 60s

Let total work = 6(A+B+C)
Also, ATQ, TW = 2(A+B+C) + 7(A+B)
Equating, we get,
C = 3(A+B)/4
Substitute this value in the expression -
= [6(A+B+C)]/C
Solve by separating A & B, everything will get cancelled and you'll get 14 hours
Solved under 60s