Question
A and B together can do a piece of work in 15 days which
B and C together can do in 20 days. After A has been working at it for 3 days and then by B for 11 days & then C finishes it in 20 days. In how many days B could finish the work?Solution
A + B = 15 days B + C = 20 days Work = L.C.M (15, 20) = 60 A + B = 4 B + C = 3 (A + B) × 3 + (B + C) × 8 + 12C = 60 4 × 3 + 3 × 8 + 12C = 60 12 + 24 + 12C = 60 12C = 60 – 36 12 C = 24 C = 2 Now, B + C = 3 B + 2 = 3 B = 1 ∴ B takes = 60/1 = 60 days
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