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 finish a work in 15 days and B can do the same work in 12 days . B worked for 8 days and left the job .In how many days, A alone can finish the remaining work?

A) 6 days B) 5 days
C) 4 days D) 3 days
 
Answer & Explanation Answer: B) 5 days

Explanation:

B's 8 days work=(1/12) x 8 = 2/3

Reaining work= 1/3

Now, 1/15 work is done by A in 1 day

Therefore, 1/3 work is done by A in 15 x (1/3) = 5 days

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11 13636
Q:

Twelve children take sixteen days to complete a work which can be completed by 8 adults in 12 days. After working for 3 days, sixteen adults left and six adults and four children joined them. How many days will they take to complete the remaining work ?

A) 3 days B) 2 days
C) 6 days D) 12 days
 
Answer & Explanation Answer: C) 6 days

Explanation:

From the given data,

12 children 16 days work,
One child’s one day work = 1/192.


8 adults 12 days work,
One adult’s one day’s work = 1/96.


Work done in 3 days = ((1/96) x 16 x 3) = 1/2


Remaining work = 1 – 1/2 = 1/2


(6 adults+ 4 children)’s 1 day’s work = 6/96 + 4/192 = 1/12

1/12 work is done by them in 1 day.

1/2 work is done by them in 12 x (1/2) = 6 days.

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11 13187
Q:

If 5 men and 2 boys working together, can do four times as much work per hour as a man and a boy together. Find the ratio of the work done by a man and that of a boy for a given time  ?

A) 1:2 B) 1:3
C) 3:1 D) 2:1
 
Answer & Explanation Answer: D) 2:1

Explanation:

5M + 2B = 4(1M + 1B)

5M + 2B = 4M + 4B

1M = 2B

The required ratio of work done by a man and a boy = 2:1

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8 13117
Q:

P alone can complete a piece of work in 6 days. Work done by Q alone in one day is equal to one-third of the work done by P alone in one day. In how many days can the work be completed if P and Q work together  ?

A) 5 (2/3) B) 6 (3/4 )
C) 4 (1/2) D) 3
 
Answer & Explanation Answer: C) 4 (1/2)

Explanation:

Work done by P alone in one day = 1/6th of the total work done by Q alone in one day = 1/3(of that done by P in one day) = 1/3(1/6 of the total) = 1/18 of the total. 

 

Work done by P and Q, working together in one day = 1/6 + 1/18  = 4/18 = 2/9 

 

They would take 9/2 days = 4 (1/2) days to complete the work working together.

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9 12784
Q:

If 34 men completed 2/5th of a work in 8 days working 9 hours a day. How many more man should be engaged to finish the rest of the work in 6 days working 9 hours a day ? 

A) 101 men B) 112 men
C) 102 men D) 120 men
 
Answer & Explanation Answer: C) 102 men

Explanation:

From the above formula i.e (m1 x t1/w1) = (m2 x t2/w2)

so, [(34 x 8 x 9)/(2/5)] = [(M x 6 x 9)/(3/5)]

so, M = 136 men

 

Number of men to be added to finish the work = 136-34 = 102 men.

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14 12719
Q:

P, Q, and R can do a job in 12 days together.  If their efficiency of working be in the ratio 3 : 8 : 5, Find in what time Q can complete the same work alone?

A) 36 days B) 30 days
C) 24 days D) 22 days
 
Answer & Explanation Answer: A) 36 days

Explanation:

Given the ratio of efficiencies of P, Q & R are 3 : 8 : 5

Let the efficiencies of P, Q & R be 3x, 8x and 5x respectively

They can do work for 12 days.

=> Total work = 12 x 16x = 192x

 

Now, the required time taken by Q to complete the job alone = 162x8x = 24 days.

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17 12718
Q:

6 boys and 8 girls can do job in 10 days , 26 boys & 48 women do work in 2 days. Find time taken by 15 boys and 20 girls to do same work ?

A) 2 days B) 3 days
C) 4 days D) 5 days
 
Answer & Explanation Answer: C) 4 days

Explanation:

One day work of 6 boys and 8 girls is given as 6b + 8g = 1/10 -------->(I)

 


One day work of 26 boys and 48 women is given as 26b + 48w = 1/2 -------->(II)

 

Divide both sides by 2 in (I) and then multiply both sides by 5

Now we get, 15b + 20g = 1/4.

Therefore, 15 boys and 20 girls can do the same work in 4 days.

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13 12293
Q:

Time taken by P alone to finish a work is 50% more than the time taken by P and Q together. Q is thrice as efficient as R. If Q and R together can complete the work in 22.5 days, then how many days will P alone take to complete the work ?

A) 17 days B) 11 days
C) 15 days D) 16 days
 
Answer & Explanation Answer: C) 15 days

Explanation:

We know that Time is inversely proportional to Efficiency

Here given time ratio of P & P+Q as

P/P+Q = 150/100 = 3:2

Efficiency ratio of P & Q as

P:Q = 2:1 ....(1)

Given Efficiency ratio of Q & R as

Q:R = 3:1 ....(2)

From (1) & (2), we get

P:Q:R = 6:3:1

P alone can finish the work in

22.5(3+1)/6 = 15 days.

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18 12193