A can do a piece of work in 80 days. He works at it for 10 days & then B alone finishes the remaining work in 42 days. In how much time will A and B, working together, finish the work? Choose the most appropriate option:
A) 30 days	B) 20 days	C) 25 days	D) 35 days	E) 45 days
Work done by A in 10 days = 10/80 = 1/8   Remaining work = (1 - (1/8)) = 7/8   Now, work will be done by B in 42 days.   Whole work will be done by B in (42 x 8/7) = 48 days   Therefore, A’s one day’s work = 1/80   B’s one day’s work = 1/48   (A+B)’s one day’s work = 1/80 + 1/48 = 8/240 = 1/30   Hence, both will finish the work in 30 days.   30 daysNSWER:30 days
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A can do a piece of work in 80 days. He works at it for 10 days & then B alone finishes the remaining work in 42 days. In how much time will A and B, working together, finish the work?