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:

Amar is 2 times as good a workman as Badal and therefore is able to finish a job in 15 days less than Badal. In how many days can they together complete the job?

A) 30 days B) 40 days
C) 10 days D) 20 days
 
Answer & Explanation Answer: C) 10 days

Explanation:
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Q:

X, Y and Z can do a piece of work in 30,40 and 50 days respectively. All three of them began the work together but Y left 4 days before completion of the work. In how many days was the work completed?

A) 660/47 B) 640/47
C) 680/47 D) 665/47
 
Answer & Explanation Answer: A) 660/47

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Q:

A takes 24 day in completing a work alone. Time taken by A in completing 1/3rd of the work is equal to the time taken by B in completing half of the work. How many days will be taken in completing the work if both A & B start working together?

A) 21/3 days B) 48 days
C) 40 days D) 48/5 days
 
Answer & Explanation Answer: D) 48/5 days

Explanation:

Ans. 
Time taken by A to complete a work alone - 24 days
Time taken by A in completing 1/3 of work = 24*1/3= 8 Days
8 day = time taken by B in completing 1/2 of work
B alone can complete the work = 16 days
The required time in completing the work if both A & B start working together?
16*24 / 40 = 48/5 Days

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Q:

A can do a work in 12 days and B in 24 days. If they work on it together for 4 days, then what fraction of work is left?

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

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Q:

A can do a work in 24 days and B in 40 days. If they work on it together for 10 days, then what fraction of work is left?

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

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Q:

A, B and C can do a job working alone in 12, 16 and 24 days respectively. In how many days they can do the job if they worked together?

A) 16/3 B) 15/4
C) 17/3 D) 19/4
 
Answer & Explanation Answer: A) 16/3

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Q:

P, Q and R together can make a table in 40 minutes. P and Q together can make it in 60 minutes. How much time (in minutes) will R alone take to make the table?

A) 100 B) 120
C) 90 D) 150
 
Answer & Explanation Answer: B) 120

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Q:

A can do a work in 15 days and B in 9 days. If they work on it together for 5 days, then what fraction of work is left?

A) 1/6 B) 3/7
C) 1/3 D) 1/9
 
Answer & Explanation Answer: D) 1/9

Explanation:
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