Question
‘A’ alone can complete a work in 15 days while
‘A’ and ‘B’ together can complete the same work in 10 days. How much percentage of the work, ‘B’ alone can complete in 21 days?Solution
Let the total work = L.C.M of 15 and 10 = 30 units Then, efficiency of ‘A’ alone = 30 ÷ 15 = 2 units/day Combined efficiency of ‘A’ and ‘B’ = 30 ÷ 10 = 3 units/day So, efficiency of ‘B’ = 3 – 2 = 1 units/day So, work done by ‘B’ alone in 21 days = 1 × 21 = 21 units So, percentage of work completed by ‘B’ = (21 ÷ 30) × 100 = 70%
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