Question
An elephant can do a work as fast as two horses ‘A’ and ‘B’ can do it by working together. If horse ‘A’ alone can complete the work in 30 hours and horse ‘B’ in 45 hours, then find the time taken by elephant to complete the work.
Solution
Let the total work = 90 units Efficiency of horse who can complete the work in 30 hours = 90/30 = 3 units/hour Efficiency of horse who can complete the work in 45 hours = 90/45 = 2 units/hour Therefore, time taken by both horses to complete the work together = 90/(3 + 2) = 18 hours Therefore, time taken by the elephant to complete the work = 24 hours
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