X, Y and Z can do a piece of work in 24, 30 and 40 days respectively. They start the work together but Z leaves 4 days before the completion of the work. In how many days is the work done?

One Answer on this Question

1. One day’s work of A, B and C = (1/24 + 1/30 + 1/40) = 1/10.

   C leaves 4 days before completion of the work, which means only A and B work during the last 4 days.

   Work done by A and B together in the last 4 days = 4 (1/24 + 1/30) = 3/10.

   Remaining Work = 7/10, which was done by A,B and C in the initial number of days.

   Number of days required for this initial work = 7 days.

   Thus, the total numbers of days required = 4 + 7 = 11 days.

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