A alone can complete a work in 14 days and B alone can complete the same work in 21 days. A and B start the work together but A leaves the work after 4 days of the starting of work. In how many days B will complete the remaining work?
Let the total work be 42 units (LCM of 14 and 21)
Efficiency of A = 42/14 = 3 units per day
Efficiency of B = 42/21 = 2 units per day
Total efficiency of A and B together = 5 units per day
Then, In 4 days, A and B will do 20 units of work.
Remaining work = 42-20 = 22 units
B can do 22 units of work in $$\dfrac{22}{2} = 11$$ days.
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