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:

After working for 8 days, Arun finds that only 13 rd of the work has been done. He employs Akhil who is 60% as efficient as Arun. How many days more would Akhil take to complete the work?

A) 24.5 days B) 26.6 days
C) 25 days D) 20 days
 
Answer & Explanation Answer: B) 26.6 days

Explanation:

Arun has completed 13rd of the work in 8 days

Then he can complete the total work in

13 ---- 8

 1 ---- ?

= 24 days


But given Akhil is only 60% as efficient as Arun

Akhil =124×60100=140

Akhil can complete the total work in 40 days

Now, remaining 2/3rd of work can be completed in

 1  ------   40

23 ------   ?  

= 26.66 days.

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Q:

50 men can build a tank in 40days, but though they begin the work together, 5 men quit every ten days. The time needed to build the tank is ?

A) 50 days B) 48 days
C) 47.5 days D) 49 days
 
Answer & Explanation Answer: A) 50 days

Explanation:

50 men can build a tank in 40 days 

Assume 1 man does 1 unit of work in 1 day

Then the total work is 50×40 = 2000 units

 

50 men work in the first 10 days and completes 50×10 = 500 units of work

45 men work in the next 10 days and completes 45×10 = 450 units of work

40 men work in the next 10 days and completes 40×10 = 400 units of work

35 men work in the next 10 days and completes 35×10 = 350 units of work

So far 500 + 450 + 400 + 350 = 1700 units of work is completed and

 

Remaining work is 2000 - 1700 = 300 units

 

30 men work in the next 10 days. In each day, they does 30 units of work.

 

Therefore, additional days required = 300/30 =10

 

Thus, total 10+10+10+10+10 = 50 days required.

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10 5473
Q:

In a hostel, there was food for 1000 students for one month. After 10 days, 1000 more students joined the hostel. How long would the students be able to carry on with the remaining food?

A) 10 days B) 15 days
C) 20 days D) 5 days
 
Answer & Explanation Answer: A) 10 days

Explanation:

After 10 days, the remaining food would be sufficient for the 1000 students for 20 more days

-->If 1000 more students are added, it shall be sufficient for only 10 days (as the no. of students is doubled, the days are halved).

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10 7282
Q:

Twenty men can do a work in eighteen days. Eighteen women can complete the same work in fifteen days. What is the ratio between the capacity of a woman and a man ?

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

Explanation:

(20 x 18) men can complete the work in in one day.

one man's one day work = 1/360

(18 x 15) women can complete the work in 1 day

1 woman's one day work = 1/270

So, required ratio = 1270:1360= 4:3

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13 8036
Q:

K can finish the work in 18 days and L can do the same work in 15 days. L worked for 10 days and left the job. In how many days, K alone can finish the remaining work ?

A) 5.5 days B) 6 days
C) 4.2 days D) 5 days
 
Answer & Explanation Answer: B) 6 days

Explanation:

L's 10 days work = 115×10=23

 


Remaining work = 1-23=13

 


Now,  work is done by K in one day = 1/18

 

1/3 work is done by K in  18×13 = 6 days

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5 3105
Q:

Raghu can complete a work in 12days working 9 hours a day. Arun can complete the same work in 8 days working 11 hours a day. If both Raghu and Arun work together, working 12 hours a day, in how many days can they complete the work ?

A)3449 days   

B)12449 days 

C)4349 days    

D)41249 days

A) Option A B) Option B
C) Option C D) Option D
 
Answer & Explanation Answer: C) Option C

Explanation:

Raghu can complete the work in (12 x 9)hrs = 108 hrs.

 

 Arun can complete the work in (8 x 11)hrs = 88 hrs.

 

Raghu's 1 hrs work = 1/108 and Arun's 1 hrs work = 1/88

 

(Raghu + Arun)'s 1 hrs work = 1108+188=492376

 
So, both Raghu and Arun will finish the work in 237649 hrs

Number of days of 12 hours each=237649×112 = 19849=4349 days

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6 6856
Q:

P and Q can do a work in 4 hours and 12 hours respectively. P starts the work at 9am and they work alternately for one hour each. When will the work be completed ?

A) 3 am B) 12 pm
C) 1 pm D) 3 pm
 
Answer & Explanation Answer: D) 3 pm

Explanation:

Work done by P and Q in the first two hours, working alternately

= First hour P + Second hour Q

14+112=13

work is completed in 2 hours

Then, the total time required to complete the work by P and Q working alternately=2 x 3= 6hours

Thus, work will be completed at 3pm.

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10 6788
Q:

K is 4 times as fast as L and working together, they can complete a work in 24 days. In how many days can L alone complete the work ?

A) 30 days B) 40 days
C) 120 days D) 80 days
 
Answer & Explanation Answer: A) 30 days

Explanation:

Given K=4L 

-->K+L = 4L+L = 5L

 

These 5L people can complete the work in 24 days, which means L alone can do the work in (24 x 5)=120 days.

 

Hence, K alone can do the work in 120/4= 30 days.

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