A can finish a work in 24 days, B in 9 days and C in 12 days. B and C start the work but are forced to leave after 3 days. The remaining work was done by A in: MCQ with Answer and Explanation
A can finish a work in 24 days, B in 9 days and C in 12 days. B and C start the work but are forced to leave after 3 days. The remaining work was done by A in:
A. 5 days
B. 10 days
C. 10.5 days
D. 6 days
Answer: Option B
Solution (By JKSSB Mock Tests)
Total work = LCM(24, 9, 12) = 72 units. Efficiency of A = 3, B = 8, C = 6. B and C work for 3 days: work done = 3 * (8 + 6) = 3 * 14 = 42 units. Remaining work = 72 - 42 = 30 units. Time taken by A to complete remaining work = 30 / 3 = 10 days.
Explanation:
Total work (LCM of 10, 12, 15) = 60 units. Efficiencies: A = 6, B = 5, C = 4. Total combined efficiency = 6 + 5 + 4 = 15 units/day. Time taken = 60 / 15 = 4 days.
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?
Explanation:
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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