Exercise : Time & Work - General Questions
✔ Time & Work -
General Questions
1.
A can do a piece of work in 10 days and B can do it in 15 days. How long will they take if they work together?
View Answer
Answer: Option B
Explanation:
Explanation:
Efficiency of A = \(1/10\), Efficiency of B = \(1/15\). Combined Efficiency = \(1/10 + 1/15 = 5/30 = 1/6\). Time taken = 6 days.
2.
A and B together can do a work in 4 days. If A alone can do it in 12 days, how long will B take alone?
View Answer
Answer: Option C
Explanation:
Explanation:
B's efficiency = \((A+B) - A = 1/4 - 1/12 = 2/12 = 1/6\). Time taken = 6 days.
3.
A, B, and C can complete a work in 12, 15, and 20 days respectively. How long will they take together?
View Answer
Answer: Option B
Explanation:
Explanation:
Total Work (LCM of 12, 15, 20) = 60 units. Efficiencies: A = 5, B = 4, C = 3. Total Efficiency = \(5 + 4 + 3 = 12\) units/day. Time = \(60 / 12 = 5\) days.
4.
A can do a work in 5 days. B is 25% more efficient than A. How many days will B take?
View Answer
Answer: Option B
Explanation:
Explanation:
Ratio of efficiency A:B = \(100 : 125 = 4 : 5\). Ratio of time = \(5 : 4\). Since A takes 5 days, B takes 4 days.
5.
A man can do a job in 15 days. His son can do it in 30 days. How long for both?
View Answer
Answer: Option B
Explanation:
Explanation:
Efficiency = \(1/15 + 1/30 = 3/30 = 1/10\). Time taken = 10 days.
6.
A can do a work in 18 days and B in 24 days. They work together for 6 days and then A leaves. How long will B take to finish the rest?
View Answer
Answer: Option C
Explanation:
Explanation:
Total Work (LCM) = 72 units. Efficiencies: A=4, B=3. 6 days work = \((4+3) \times 6 = 42\) units. Remaining = \(72 - 42 = 30\) units. B's time for remaining = \(30 / 3 = 10\) days.
7.
A and B can do a job in 12 days, B and C in 15 days, and C and A in 20 days. How long for all three together?
View Answer
Answer: Option B
Explanation:
Explanation:
\(2(A+B+C) = 1/12 + 1/15 + 1/20 = 12/60 = 1/5\). \((A+B+C) = 1/10\). Time taken = 10 days.
8.
A can do a work in 10 days and B in 20 days. They work together but A leaves 2 days before completion. Total time?
View Answer
Answer: Option C
Explanation:
Explanation:
Let total time be \(x\). B worked for \(x\) days, A for \((x-2)\) days. \((x-2)/10 + x/20 = 1 \implies 2x - 4 + x = 20 \implies 3x = 24 \implies x = 8\) days.
9.
12 men can complete a work in 16 days. How many men are needed to finish it in 24 days?
View Answer
Answer: Option B
Explanation:
Explanation:
\(M_1D_1 = M_2D_2 \implies 12 \times 16 = M_2 \times 24 \implies M_2 = 192/24 = 8\) men.
10.
A is thrice as good a workman as B. A takes 60 days less than B to finish a job. Find the time for B.
View Answer
Answer: Option C
Explanation:
Explanation:
Efficiency A:B = \(3:1\). Time A:B = \(1:3\). Difference in time units = \(2 \to 60\) days. 1 unit = 30. B's time (3 units) = 90 days.