A can complete a work in 19 days and B in 19 days. If both work together, in how many days will the work be completed? MCQ with Answer and Explanation
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Question #1
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A can do a piece of work in 25 days and B can finish it in 20 days. They work together for 5 days and then A leaves. In how many days will B finish the remaining work?
Correct Answer: Option A
Explanation:
Total work = LCM(25, 20) = 100 units. Efficiency of A = 4, B = 5. Combined efficiency = 9 units/day. In 5 days, work done = 5 * 9 = 45 units. Remaining work = 100 - 45 = 55 units. Time taken by B to complete remaining work = 55 / 5 = 11 days.
Total work = LCM(25, 20) = 100 units. Efficiency of A = 4, B = 5. Combined efficiency = 9 units/day. In 5 days, work done = 5 * 9 = 45 units. Remaining work = 100 - 45 = 55 units. Time taken by B to complete remaining work = 55 / 5 = 11 days.
This question belongs to:
Maths
Time and Work
Question #2
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A can complete a work in 10 days and B can complete the same work in 30 days. If they work together, in how many days will the work be completed?
Correct Answer: Option B
Explanation:
Combined rate = 1/10 + 1/30. Time = 1 ÷ combined rate = 7.5 days.
Combined rate = 1/10 + 1/30. Time = 1 ÷ combined rate = 7.5 days.
This question belongs to:
Maths
Time and Work
Question #3
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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?
Correct Answer: Option D
Explanation:
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.
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.
This question belongs to:
Maths
Time and Work
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