Time and Work
Q1
12 man can do a piece of work in 25 days.How long will 10 men take to complete the work?
Ans: 12 X 25 / 10 = 30
Q2
30 man can do a piece of work in 36 days.What is the number of men needed to complete the same work in 24 days?
Ans: 30 X 36 / 24 = 45
Q3
12 man can do a piece of work in 18 days.What is the extra number of men needed to complete the same work in 8 days?
Ans: The number of men needed to complete the work in 8 days = 12 X 18 / 8 = 27
Number of men needed extra = 27  12 = 15
Q4
80 man can do a piece of work in 90 days.If 20 more men joined with them how long will take to complete the work?
Ans: 80 X 90 / (80+20) = 72 days
Q5
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 ?
Ans:
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 
Q6
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:
Ans:
(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 
Q7
If 6 men and 8 boys can do a piece of work in 10 days while 26 men and 48 boys can do the same in 2 days, the time taken by 15 men and 20 boys in doing the same type of work will be: Ans:
15 men and 20 boys can do the work in 4 days. Q8

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