Time and Work Questions

FACTS  AND  FORMULAE  FOR  TIME  AND  WORK  QUESTIONS

 

 

1. If A can do a piece of work in n days, then A's 1 day's work =1n

2. If A’s 1 day's work =1n, then A can finish the work in n days.

 

3. A is thrice as good a workman as B, then:

Ratio of work done by A and B = 3 : 1.

Ratio of times taken by A and B to finish a work = 1 : 3.

 

NOTE : 

Efficiency1No of time units

 

 Efficiency × Time = Constant Work

 

Hence, Required time = WorkEfficiency

 

Whole work is always considered as 1, in terms of fraction and 100% , in terms of percentage.

In general, number of day's or hours = 100Efficiency

Q:

A can do a piece of work in 10 days, B in 15 days. They work together for 5 days, the rest of the work is finished by C in two more days. If they get Rs. 3000 as wages for the whole work, what are the daily wages of A, B and C respectively (in Rs):

A) 200, 250, 300 B) 300, 200, 250
C) 200, 300, 400 D) None of these
 
Answer & Explanation Answer: B) 300, 200, 250

Explanation:

A's 5 days work = 50% 

 

B's 5 days work = 33.33%

 

C's 2 days work = 16.66%          [100- (50+33.33)]

 

 Ratio of contribution of work of A, B and C = 50 : 3313 : 1623 

 

                                                               = 3 : 2 : 1  

 

A's total share = Rs. 1500

 

B's total share = Rs. 1000

 

C's total share = Rs. 500 

 

A's one day's earning = Rs.300 

 

B's one day's earning = Rs.200 

 

C's one day's earning = Rs.250

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88 31753
Q:

Relation Between Efficiency and Time

A is twice as good a workman as B and is therefore able to finish a piece of work in 30 days less than B.In how many days they can complee the whole work; working together?

Answer

Sol:       Ratio of efficiency = 2:1 (A:B)


 


       Ratio of required time = 1:2 (A:B)  => x:2x


 


       but    2x-x=30  


 


       x= 30  and  2x= 60


 


       Now   efficiency of A =3.33%  and efficiency of B =1.66%


 


       Combined efficiency of A and B together = 5%


 


       time required by A and B working together to finish the work = 20 days


 


Note:      Efficiency inversely proportional to Time


 


  Therefore, Efficiency x time = Constant Work


 


             Hence, Required time


 


whole work is always cosidered as 1, in terms of fraction and 100%, in terms of percentage.


 


In, general no.of days or hours =  Efficiency x time

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38 22456
Q:

12 men can complete a work in 8 days. 16 women can complete the same work in 12 days. 8 men and 8 women started working  and worked for 6 days. How many more men are to be added to complete the remaining work in 1 day?

A) 8 B) 12
C) 16 D) 24
 
Answer & Explanation Answer: B) 12

Explanation:

1 man's 1 day work =1/96 ; 1 woman's 1 day work = 1/192

Work done in 6 days=6896+8192=6×18 =34 

Remaining work = 1/4

(8 men +8 women)'s 1 day work = 1896+8192 =1/8

Remaining work =1/4 -  1/8 = 1/8

 

 1/96 work is done in 1 day by 1 man

 

Therefore, 1/8 work will be done in 1 day by 96 x (1/8) =12 men

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64 21470
Q:

A, B and C can do a piece of work in 24 days, 30 days and 40 days respectively. They began the work together but C left 4 days before the completion of the work. In how many days was the work completed?

A) 11 days B) 12 days
C) 13 days D) 14 days
 
Answer & Explanation Answer: A) 11 days

Explanation:

One day's work of A, B and C = (1/24 + 1/30 + 1/40) = 1/10

C leaves 4 days before completion of the work, which means only A and B work during the last 4 days.

Work done by A and B together in the last 4 days = 4 (1/24 + 1/30) = 3/10

Remaining Work = 7/10, which was done by A,B and C in the initial number of days. 

Number of days required for this initial work = 7 days.

Thus, the total numbers of days required = 4 + 7 = 11 days.

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41 20141
Q:

P can complete a work in 12 days working 8 hours a day.Q can complete the same work in 8 days working 10 hours a day. If both p and Q work together,working 8 hours a day,in how many days can they complete the work?

A) 60/11 B) 61/11
C) 71/11 D) 72/11
 
Answer & Explanation Answer: A) 60/11

Explanation:

P can complete the work in (12 * 8) hrs = 96 hrs

Q can complete the work in (8 * 10) hrs=80 hrs

Therefore, P's 1 hour work=1/96   and Q's 1 hour work= 1/80

(P+Q)'s 1 hour's work =(1/96) + (1/80) = 11/480

so both P and Q will finish the work in 480/11 hrs  

Therefore, Number of days of 8 hours each = (480/11) x (1/8) = 60/11

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15 11069
Q:

A and  B can do  a piece of work in 30 days , while  B and C can do the same work in 24 days and C and A in 20 days . They all work together for 10 days when B and C leave. How many days more will A take to finish  the work?

A) 18 days B) 24 days
C) 30 days D) 36 days
 
Answer & Explanation Answer: A) 18 days

Explanation:

2(A+B+C)'s 1 day work = 1/30 + 1/24 + 1/20 = 1/8

=>(A+B+C)'s  1 day's work= 1/16

work done by A,B and C in 10 days=10/16 = 5/8

Remaining work= 3/8

A's 1 day's work= 116-124=148

Now, 1/48 work is done by A in 1 day.

 So, 3/8 work  wil be done by A in =48 x (3/8) = 18 days

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17 10156
Q:

A can do a certain work in the same time in which B and C together can do it.If A and B together could do it in 20 days and C alone in 60 days ,then B alone could do it in:

A) 20days B) 40 days
C) 50 days D) 60 days
 
Answer & Explanation Answer: D) 60 days

Explanation:

(A+B)'s 1 day's work=1/20

C's 1 day work=1/60

(A+B+C)'s 1 day's work= 1/20 + 1/60 = 1/15

Also A's 1 day's work =(B+C)'s 1 day's work

 

Therefore,  we get: 2 * (A's 1 day 's work)=1/15

=>A's 1 day's work=1/30

 

Therefore, B's 1 day's work= 1/20 - 1/30 = 1/60

So, B alone could do the work in 60 days.

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24 8661
Q:

A works twice as fast as B.If  B can complete a work in 18 days independently,the number of days  in which A and B can together finish the work is:

A) 4 days B) 6 days
C) 8 days D) 10 days
 
Answer & Explanation Answer: B) 6 days

Explanation:

Ratio of rates of working of A and B =2:1. So, ratio of times taken =1:2

Therefore, A's 1 day's work=1/9 

B's 1 day's work=1/18 

(A+B)'s 1 day's work= 1/9 + 1/18 = 1/6

so, A and B together can finish the work in 6 days

 

 

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