Exercise : Time & Work - General Questions
✔ Time & Work -
General Questions
21.
A can finish a work in 20 days and B in 30 days. They work together but A's efficiency drops by 20% and B's drops by 10% due to illness. Total time?
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Answer: Option B
Explanation:
Explanation:
Original Eff: A=3, B=2 (Total 60). New Eff: \(A=2.4, B=1.8\). Combined = 4.2. Time = \(60 / 4.2 = 14.28\) days.
22.
2 men and 1 woman can do a piece of work in 14 days, while 4 women and 2 men can do it in 8 days. Find the ratio of efficiency of Man to Woman.
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Answer: Option B
Explanation:
Explanation:
\(14(2M + 1W) = 8(2M + 4W) \implies 28M + 14W = 16M + 32W \implies 12M = 18W\). Ratio M:W = 3:2.
23.
Contractor takes a job to build a road in 120 days and employs 100 men. After 45 days, only 1/4 of work is done. How many extra men needed to finish on time?
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Answer: Option B
Explanation:
Explanation:
Work left = 3/4. Days left = 75. \(\frac{100 \times 45}{1/4} = \frac{M_2 \times 75}{3/4} \implies 18000 = 100M_2 \implies M_2 = 180\). Extra men = \(180 - 100 = 80\).
24.
A and B together can do a work in 12 days. A works for 8 days and B finishes the rest in 20 days. How long for B alone?
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Answer: Option C
Explanation:
Explanation:
\(8A + 20B = 12(A+B) \implies 8A + 20B = 12A + 12B \implies 8B = 4A \implies A = 2B\). Combined Eff = \(2B + B = 3B\). \(3B \times 12 \text{ days} = 36B\) (Total Work). B alone = \(36B / B = 36\) days.
25.
A certain number of men can do a work in 60 days. If there were 8 men more, it could be finished in 10 days less. Original number of men?
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Answer: Option B
Explanation:
Explanation:
\(x \times 60 = (x+8) \times 50 \implies 6x = 5x + 40 \implies x = 40\) men.