A, B and C can complete a piece of work in 10, 15 and 20 days respectively. They started together but A left after 2 days and B left 2 days before the completion of the work. Find the total number of days taken to complete the work. MCQ with Answer and Explanation
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Question #1
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A can complete a work in 17 days and B in 34 days. After working together for 5 days, what percentage of work remains?
Correct Answer: Option B
Explanation:
Remaining work = (1 - 5*(1/17+1/34))×100 = 55.88%.
Remaining work = (1 - 5*(1/17+1/34))×100 = 55.88%.
This question belongs to:
Maths
Time and Work
Question #2
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A is 50% more efficient than B. C does half of the work done by A and B together in the same time. If C alone can do the work in 40 days, then A, B and C together can do the work in:
Correct Answer: Option C
Explanation:
Let efficiency of B = 2, then efficiency of A = 3. Combined efficiency of A and B = 5. Efficiency of C = 5 / 2 = 2.5. Total work = Efficiency of C * Time taken by C = 2.5 * 40 = 100 units. Combined efficiency of A, B and C = 3 + 2 + 2.5 = 7.5 units/day. Time taken together = 100 / 7.5 = 1000 / 75 = 40 / 3 = 13(1/3) days.
Let efficiency of B = 2, then efficiency of A = 3. Combined efficiency of A and B = 5. Efficiency of C = 5 / 2 = 2.5. Total work = Efficiency of C * Time taken by C = 2.5 * 40 = 100 units. Combined efficiency of A, B and C = 3 + 2 + 2.5 = 7.5 units/day. Time taken together = 100 / 7.5 = 1000 / 75 = 40 / 3 = 13(1/3) days.
This question belongs to:
Maths
Time and Work
Question #3
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A can complete a work in 12 days and B can complete the same work in 17 days. If they work together, in how many days will the work be completed?
Correct Answer: Option D
Explanation:
Combined rate = 1/12 + 1/17. Time = 1 ÷ combined rate = 7.03 days.
Combined rate = 1/12 + 1/17. Time = 1 ÷ combined rate = 7.03 days.
This question belongs to:
Maths
Time and Work
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