A can do a work in 19 days and B in 23 days. In how many days will they complete 75% of the work together? MCQ with Answer and Explanation
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Question #1
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A can build a wall in 30 days, while B can destroy it in 40 days. If they work on alternate days starting with A, in how many days will the wall be built?
Correct Answer: Option B
Explanation:
Total work = LCM(30, 40) = 120 units. Efficiency of A = +4, B = -3. In 2 days, net work = 4 - 3 = 1 unit. We look for when the work reaches 120 - 4 = 116 units. 116 units are done in 116 * 2 = 232 days. On the 233rd day, A works and completes 4 units, making total work 116 + 4 = 120 units. Thus, the wall is completed in 233 days.
Total work = LCM(30, 40) = 120 units. Efficiency of A = +4, B = -3. In 2 days, net work = 4 - 3 = 1 unit. We look for when the work reaches 120 - 4 = 116 units. 116 units are done in 116 * 2 = 232 days. On the 233rd day, A works and completes 4 units, making total work 116 + 4 = 120 units. Thus, the wall is completed in 233 days.
This question belongs to:
Maths
Time and Work
Question #2
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A can complete a work in 31 days and B in 24 days. If both work together, in how many days will the work be completed?
Correct Answer: Option B
Explanation:
Combined rate = 1/31 + 1/24. Time = 13.53 days.
Combined rate = 1/31 + 1/24. Time = 13.53 days.
This question belongs to:
Maths
Time and Work
Question #3
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A can do a work in 9 days and B in 23 days. In how many days will they complete 75% of the work together?
Correct Answer: Option A
Explanation:
Combined time for full work multiplied by 0.75 = 4.85 days.
Combined time for full work multiplied by 0.75 = 4.85 days.
This question belongs to:
Maths
Time and Work
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