A, B and C can complete a work in 12, 15 and 20 days respectively. If they work together, in how many days will the work be completed? MCQ with Answer and Explanation
A, B and C can complete a work in 12, 15 and 20 days respectively. If they work together, in how many days will the work be completed?
A. 4.5 days
B. 6 days
C. 5 days
D. 4 days
Answer: Option C
Solution (By JKSSB Mock Tests)
Total work = LCM(12, 15, 20) = 60 units. Efficiency of A = 5, B = 4, C = 3. Combined efficiency = 5 + 4 + 3 = 12 units/day. Time taken together = 60 / 12 = 5 days.
A can do a piece of work in 40 days. He works at it for 8 days and then B finishes it in 16 days. How long will A and B together take to complete the work?
Explanation:
Let total work be 40 units. Efficiency of A = 1 unit/day. In 8 days, A completes 8 units. Remaining work = 40 - 8 = 32 units. B finishes 32 units in 16 days, so B's efficiency = 32 / 16 = 2 units/day. Combined efficiency of A and B = 1 + 2 = 3 units/day. Time taken together = 40 / 3 = 13(1/3) days.
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