: SI recruitment exam: Manage your calculation time for this section #IndiaNEWS #Education By Banda Ravipal Reddy Director, SIGMA Sai Institute of General Mental Ability Hyderabad This is in continuation

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SI recruitment exam: Manage your calculation time for this section #IndiaNEWS #Education
By Banda Ravipal Reddy
Director, SIGMA
Sai Institute of General Mental Ability
Hyderabad
This is in continuation to the last article on preparation for the Sub-Inspector of Police recruitment exam. Here are some practice questions and explanations on the Time and Work topic. To improve calculations speed, the aspirants must practice questions from the previous question papers.
1. X and Y can do a piece of work in 10 days and 12 days respectively. If they work alternate days starting with X, the work will be finished in ___ days.
A. 10 1/6 B. 10 5/6 C. 10 7/6 D. 10 5/9
Ans:B
Explanation:
(A B)’s 2 day work is= 1/10 1/12= 6 5/60 =11/60.
Work done in 5 pairs of days= 5× 11/60.
Remaining work=1- 55/60= 5/60
On 11th day it’s A turn,
∴ 5/60 Work is done by A=10× 5/60 = 5/6 days.
Total time taken=10 5/6=10 5/6 days.
2. A started a work and left after 2 days. Then B finished the work in 9 days. Had A left the work after working for 3 days, B would have finished the work in 6 days. Each of them working alone finish the whole work in ____ days.
A. 5, 15 B. 15, 5 C. 6, 9 D. 9, 6
Ans: A
Explanation:
Let A finish the work in X days & B finish the work in Y days
2/x 9/y =1 & 3/x 6/y=1
∴by solving, 3/x-2/y= 6/y-9/y
Y=3X
By substituting Y value, will get X=5 & Y=15.
3. A, B and C can do a piece of work in 16 days, 24,days and 32 days viz. They started the work together but A left after 4 days and B left 3 days before the completion. The work will be completed in ___ days
A. 10 B. 12 C. 8 D. 7
Ans:B
Explanation:
(A B C)’s 1day work = 1/16 1/24 1/32 = 6 4 3/96 = 13/96
(A B C)’s 4 day work = 4× 13/96 = 52/96
Work done by C in 3 days = 1/32 ×3 = 3/32
. Remaining work =1-( 52/96 3/32)
=1-(52 9/96 ) = 35/96
B and C can do 7 units of work per a day
∴ 35 units work can do in= 35/7 = 5 days.
The work will be completed in =4 3 5=12 days.
4. A takes as much time as B and C together take to do the work. A and B together can do it in 20 days. If C alone can do in 30 days, B alone can do it in _____ days.
A. 100 B. 110 C. 120 D. 130
Ans: C
Explanation:
Given, A=B C
C = 1/30
(A B)’s 1 day work= 1/20
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