Question
Working alone, B can complete the work in 30 days. C is
twice as efficient as B and A takes 3 days more than it takes C to complete the work. Working together, in how much time would they be able to complete 7 such works?Solution
Time taken by B to complete the work = 30 days Time taken by C to complete the work = 30/2 = 15 days Time taken by A to complete the work alone = 15 + 3 = 18 days Work done by A, B and C together in 1 day. ⇒ (1/30 + 1/15 + 1/18) = (3 + 6 + 5)/90 = 14/90 this means if would take 45/7 days for A, B and C to complete the work together ∴ Time taken A, B and C to complete 7 works = 7 × 45/7 days = 45 days
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