Question 60

A can finish a work in 20 days and B can finish the same work in 25 days. They begin together, but B left the work after 5 days. How many more days will A take to finish the remaining work?

Solution

Let the total work be 100 units.

($$\because LCM of 20 and 25 is 100.$$)

Efficiency of A = work/time = 100/20 = 5 unit/day

Efficiency of B = 100/25 = 4 unit/day

Work done by A and B in 5 days = efficiency $$\times times = (4 + 5) \times$$ 5 = 45 units

Remaining work = 100 - 45 = 55 units

Time taken by A to complete 55 units work = 55/5 = 11 days

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