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Hyderabad: This article is in continuation to the last article on preparation for the Sub-Inspector of Police recruitment exam. Here are some previous year questions and explanations on the Time and Work topic. To improve calculations speed, the aspirants must practice questions from the previous question papers. 1. A can do a piece of work […]
Hyderabad: This article is in continuation to the last article on preparation for the Sub-Inspector of Police recruitment exam. Here are some previous year questions and explanations on the Time and Work topic. To improve calculations speed, the aspirants must practice questions from the previous question papers.
1. A can do a piece of work in 4 hours. B and C together take 3 hours, A and C together take 2 hours to do it. The time taken for B to complete the work is (in hours) (SI 2016)
A.10 B. 12 C. 8 D. 9
Ans: B
Explanation:
A’s1 hour work = 1/4
(B C)’s 1 hour work = 1/3
(A C)’s 1 hour work = 1/2
Therefore, C’s 1 hour work = 1/2 – 1/4 = 1/4
B’s 1 hour work =1/3 – 1/4 = 1/12
Hence, B will complete the whole work in 12 days.
2. A contractor undertook to finish a certain work in 124 days and employed 120 men on it. After 64 days, he found that he had already done 2/3 of the work. The number of men he can discharge now so that the work may finish in time is (SI 2016)
A. 24 B. 56 C. 64 D. 80
Ans: B
Explanation:
Remaining work = 1- 2/3 = 1/3
Remaining days = 124 – 64 = 60
According to the formula
M1D1/W1= M2D2/W2
(120×64)/(2/3) = (M2 ×60)/(1/3)
M2 = (120×64)/(2×60) = 64
Therefore, no. of men can be discharged = 120 – 64 = 56 men
3. A and B undertook to do a piece of work for Rs 4,500. A alone could do it in 8 days and B alone in 12 days. With the assistance of C they finished the work in 4 days. The C’s share of money is (in rupees) (SI 2016)
A. 2,250 B. 1,500 C. 750 D. 375
Ans: C
Explanation:
A= 8 days, B = 12 days and A B C = 4 days
LCM of (A, B, A B C) is = 24
Efficiency of (A, B, A B C) = 3, 2 and 6
A B C=6
Efficiency of C= 6-3-2 = 1
Ratio of efficiency of A, B, C = 3: 2: 1
Total amount = 4500
C’s share= 4500×1/6 = 750
4. Seven young men and four boys can complete a work in 6 days. A young man completes double the work than a boy in a day. The number of days that five men and four boys require to complete the work is (SI 2016)
A.5 B. 4 C. 6 D. 54/7
Ans: D
Explanation:
Given: Time taken by 7 men and 4 boys to finish a work = 6 days
Work of a young man = 2 × work of the boy
Let M be the work done by a men and N be the work done by a boy in one day.
According to the question, M = 2N ⇒ M/N = 2/1
Let M = 2 unit and N = 1 unit
Total work = (7 × 2 4 × 1) × 6 ⇒ 108 unit
Time taken by 5 men and 4 boy to complete this work = 108/(5 × 2 4 × 1) ⇒ 108/14 ⇒ 54/7
The number of days that five men and four boys require to complete the work is 54/7.
By
Banda Ravipal Reddy
Director, SIGMA
Sai Institute of General Mental Ability
Hyderabad
