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A and B can do a piece of work in 72 days. B and C can do it in 120 days. A and C can do it in 90 days. In what time can A alone do it?
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Explanation:
(A + B)’s 1 day’s work = 1 / 72
(B + C)’s 1 day’s work = 1/120
(A + C)’s 1 day’s work = 1 /90
2(A + B + C)’s 1 day’s work =1\72+1\120+1\90
(A + B + C)’s 1 day’s work = 5+3+4\360X2=12\360X2=1\60
A’s 1 day’s work = (A + B + C)’s 1 day’s work – (B + C)’s 1 day’s work
=1\60−1\120=2−1\120=1\120
A alone can finish the work in 120 days.