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1. Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. The number of hours taken by C alone to fill the tank is:
Remaining part = =
∴ (A + B)'s 7 hour's work =
(A + B)'s 1 hour's work =
∴ C's 1 hour's work = {(A + B + C)'s 1 hour's work} - {(A + B's 1 hour's work}
∴ C alone can fill the tank in 14 hours
Solution:
Part filled in 2 hours = = Remaining part = =
∴ (A + B)'s 7 hour's work =
(A + B)'s 1 hour's work =
∴ C's 1 hour's work = {(A + B + C)'s 1 hour's work} - {(A + B's 1 hour's work}
∴ C alone can fill the tank in 14 hours