A and B can do a piece of work in 20 days and 12 days respectively. A started the work alone and then after 4 days B joined him till the completion of the work. How long did the work last? MCQ with Answer and Explanation
A and B can do a piece of work in 20 days and 12 days respectively. A started the work alone and then after 4 days B joined him till the completion of the work. How long did the work last?
A. 12 days
B. 6 days
C. 8 days
D. 10 days
Answer: Option D
Solution (By JKSSB Mock Tests)
Total work = LCM(20, 12) = 60 units. Efficiency of A = 3, B = 5. In 4 days, A alone completes = 4 * 3 = 12 units. Remaining work = 60 - 12 = 48 units. Combined efficiency of A and B = 3 + 5 = 8. Time taken together for remaining work = 48 / 8 = 6 days. Total duration of work = 4 + 6 = 10 days.
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