# Aptitude - Time and Work

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 :

 1 4

 1 10

 7 15

 8 15

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

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:

 9 1 days 5

 9 2 days 5

 9 3 days 5

10
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 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

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?
12 days
15 days
16 days
18 days
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.

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:
20 days
 22 1 days 2
25 days
30 days
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

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?
Rs. 375
Rs. 400
Rs. 600
Rs. 800
 C's 1 day's work = 1 - 1 + 1 = 1 - 7 = 1 . 3 6 8 3 24 24 C's share (for 3 days) = Rs. 3 x 1 x 3200 = Rs. 400. 24