[Q] A and B working together can complete a work in 15 days and 10 days respectively. They
started doing the work together but after 2 days B leaves and A
alone completes the remaining work. The whole work was completed in how many days?
(a) 16 days
(b) 18 days
(c) 14 days
(d) 12 days
(a) 16 days
(b) 18 days
(c) 14 days
(d) 12 days
Solution
Answer
(d)
Explanation
----
Work done by A in 1 day = 1/15
Work done by B in 1 day = 1/10
Work done by A and B in 1 day = 1/15 + 1/10 = 1/6
Work done by A and B in 2 days = 2 × (1/6) = 1/3
Remaining work = 1 – 1/3 = 2/3
Time taken by A to complete the remaining work 2/3 = (2/3) / (1/15) = 10 days
Total time taken = 2 + 10 = 12 days
Explanation
----
Work done by A in 1 day = 1/15
Work done by B in 1 day = 1/10
Work done by A and B in 1 day = 1/15 + 1/10 = 1/6
Work done by A and B in 2 days = 2 × (1/6) = 1/3
Remaining work = 1 – 1/3 = 2/3
Time taken by A to complete the remaining work 2/3 = (2/3) / (1/15) = 10 days
Total time taken = 2 + 10 = 12 days
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