A and B can do a piece of work in 15 days and 10 days respectively. They started the work together, but A left after 2 days. In how many days will B complete the remaining work? MCQ with Answer and Explanation
A and B can do a piece of work in 15 days and 10 days respectively. They started the work together, but A left after 2 days. In how many days will B complete the remaining work?
A. 7 days
B. 6 days
C. 5 days
D. 6(2/3) days
Answer: Option D
Solution (By JKSSB Mock Tests)
Total work = LCM(15, 10) = 30 units. Efficiency of A = 2, B = 3. Combined efficiency = 5. In 2 days, work done = 2 * 5 = 10 units. Remaining work = 30 - 10 = 20 units. Time taken by B to complete remaining work = 20 / 3 = 6(2/3) days.
Explanation:
Let efficiency of C = 1. Then efficiency of B = 3 * 1 = 3. Efficiency of A = 2 * 3 = 6. Total work = Efficiency of C * Time of C = 1 * 24 = 24 units. Combined efficiency of A, B and C = 6 + 3 + 1 = 10. Time taken together = 24 / 10 = 2.4 days.
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