A, B and C can complete a work in 10, 12 and 15 days respectively. They start working together. Find the number of days required to complete the work. MCQ with Answer and Explanation
A, B and C can complete a work in 10, 12 and 15 days respectively. They start working together. Find the number of days required to complete the work.
A. 5 days
B. 4 days
C. 3 days
D. 6 days
Answer: Option B
Solution (By JKSSB Mock Tests)
Total work = LCM(10, 12, 15) = 60 units. Efficiency of A = 6, B = 5, C = 4. Combined efficiency = 6 + 5 + 4 = 15 units/day. Time taken = 60 / 15 = 4 days.
A and B together can do a piece of work in 9 days. If A does thrice the work of B in a given time, how many days will A alone take to complete the total work?
Explanation:
Ratio of efficiency of A : B = 3 : 1. Combined efficiency = 3 + 1 = 4. Total work = 9 * 4 = 36 units. Time taken by A alone = 36 / 3 = 12 days.
A can finish a work in 12 days and B can do it in 15 days. After A had worked for 3 days, B also joined him to finish the remaining work. In how many days was the remaining work completed?
Explanation:
Total work = LCM(12, 15) = 60 units. Efficiency of A = 5, B = 4. In 3 days, A completed 3 * 5 = 15 units. Remaining work = 60 - 15 = 45 units. Combined efficiency of A and B = 5 + 4 = 9 units/day. Time taken for remaining work = 45 / 9 = 5 days.
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