1.
A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is :
A.
1
4
B.
1
10
C.
7
15
D.
8
15
Answer & Explanation
Answer: Option D
Explanation:
A’s 1 day’s work = 1 ;
15
B’s 1 day’s work = 1 ;
20
(A + B)’s 1 day’s work = ( 1 + 1 ) = 7 .
15 20 60
(A + B)’s 4 day’s work = ( 7 x 4 ) = 7 .
60 15
Therefore, Remaining work = ( 1 – 7 ) = 8 .
15 15
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2.
A can lay railway track between two given stations in 16 days and B can do the same job in 12 days. With help of C, they did the job in 4 days only. Then, C alone can do the job in:
A.
9 1 days
5
B.
9 2 days
5
C.
9 3 days
5
D. 10
Answer & Explanation
Answer: Option C
Explanation:
(A + B + C)’s 1 day’s work = 1 ,
4
A’s 1 day’s work = 1 ,
16
B’s 1 day’s work = 1 .
12
Therefore C’s 1 day’s work = 1 – ( 1 + 1 ) = ( 1 – 7 ) = 5 .
4 16 12 4 48 48
So, C alone can do the work in 48 = 9 3 days.
5 5
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3.
A, B and C can do a piece of work in 20, 30 and 60 days respectively. In how many days can A do the work if he is assisted by B and C on every third day?
A. 12 days B. 15 days
C. 16 days D. 18 days
Answer & Explanation
Answer: Option B
Explanation:
A’s 2 day’s work = 1 x 2 = 1 .
20 10
(A + B + C)’s 1 day’s work = 1 + 1 + 1 = 6 = 1 .
20 30 60 60 10
Work done in 3 days = 1 + 1 = 1 .
10 10 5
Now, 1 work is done in 3 days.
5
Whole work will be done in (3 x 5) = 15 days.
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4.
A is thrice as good as workman as B and therefore is able to finish a job in 60 days less than B. Working together, they can do it in:
A. 20 days B.
22 1 days
2
C. 25 days D. 30 days
Answer & Explanation
Answer: Option B
Explanation:
Ratio of times taken by A and B = 1 : 3.
The time difference is (3 – 1) 2 days while B take 3 days and A takes 1 day.
If difference of time is 2 days, B takes 3 days.
If difference of time is 60 days, B takes 3 x 60 = 90 days.
2
So, A takes 30 days to do the work.
A’s 1 day’s work = 1
30
B’s 1 day’s work = 1
90
(A + B)’s 1 day’s work = 1 + 1 = 4 = 2
30 90 90 45
A and B together can do the work in 45 = 22 1 days.
2 2
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5.
A alone can do a piece of work in 6 days and B alone in 8 days. A and B undertook to do it for Rs. 3200. With the help of C, they completed the work in 3 days. How much is to be paid to C?
A. Rs. 375 B. Rs. 400
C. Rs. 600 D. Rs. 800
Answer & Explanation
Answer: Option B
Explanation:
C’s 1 day’s work = 1 – 1 + 1 = 1 – 7 = 1 .
3 6 8 3 24 24
A’s wages : B’s wages : C’s wages = 1 : 1 : 1 = 4 : 3 : 1.
6 8 24
C’s share (for 3 days) = Rs. 3 x 1 x 3200 = Rs. 400.