84 persons take 56 days to complete a certain task. when 1/4 of the task was completed, one-seventh of the workers left. how many days in all does it take to complete the entire task?
A)60
B)64
C)63
D)61

Solution:Total work=Total person×Total daysTotal work=84×56=4704 units14th work=47044=1176 units14th work will take 14×56=14 days.Work left=4704-1176=3528 units17th worker=847=12 workers leftTotal worker remained=84-12=72 daysTherefore, total work remaining=3528 units ; total worker remained=723528=total time×72total time=49Therefore, total time needs to be completed=49+14=63 daysOption C

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