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1. A and B can do a piece of work in 72 days, B and C can do it in 120 days and A and C can do it in 90 days. In how many days all three together can do the work ?
Here L.C.M. of Total Work = 360
One day work of A + B = = 5 unit/day
One day work of B + C = = 3 unit/day
One day work of C + A = = 4 unit/day
∴ Total units/day = 5 + 3 + 4 = 12
(Here , 12 unit represents twice of the work done by A, B and C. So we will divide it by 2)
Work done by (A + B + C) per day = = 6 units/day
∴Total time taken by (A + B + C)
Solution:
In these kind of questions, always take total work as L.C.M. of number of days.Here L.C.M. of Total Work = 360
One day work of A + B = = 5 unit/day
One day work of B + C = = 3 unit/day
One day work of C + A = = 4 unit/day
∴ Total units/day = 5 + 3 + 4 = 12
(Here , 12 unit represents twice of the work done by A, B and C. So we will divide it by 2)
Work done by (A + B + C) per day = = 6 units/day
∴Total time taken by (A + B + C)