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:

Raghu can do a job in 12 days alone and Sam can do the same job in 15 days alone. A third person Aru whose efficiency is two-third of efficiency of both Ram and Shyam together, can do the same job in how many days alone?

A) 10 B) 12
C) 13 D) 15
 
Answer & Explanation Answer: A) 10

Explanation:

One day work of Raghu and Sam together = 1/12 + 1/15 = 9/60 = 3/20

Aru efficiency = 2/3 of (Raghu + Sam)

Number of days required for Aru to do thw work alone = 3/2 x 20/3 = 10 days. 

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9 5552
Q:

A and B can do a piece of work for Rs 1540. Find the difference between the wages of C and B for the same work If A can do the work in 12 days and B can do the same work in 8 days and with the help of C, A and B can do the same work in 2 days?

A) 980 B) 1232
C) 810 D) 1121
 
Answer & Explanation Answer: B) 1232

Explanation:

From the given data,


                       Day      Capacity

A              ->    12          2

B              ->     8           3             2

A + B + C ->     2            12

=> Capacity of C = 12 - 5 = 7

Ratio of capacity of A : B : C = 2 : 3 : 7

Difference of wages of C & B = 4/5 x 1540

= 4 x 308 = Rs. 1232

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13 5394
Q:

10 boys can complete a work in 7 days and 10 girls take 14 days to complete the work. How many days will 5 boys and 10 girls take to complete the work ?

A) 13 days B) 10 days
C) 7 days D) 16 days
 
Answer & Explanation Answer: C) 7 days

Explanation:

1 boy's 1 day work = 1/70

1 girl's 1 day work = 1/140

(5 boys + 10 girls)'s 1 day work = (5/70 + 10/140) = (1/14 + 1/14) = 1/7

 

5 boys and 10 girls will complete the work in 7 days.

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2 5270
Q:

Priya can do a work in 16 days. In how many days will the work be completed by Sai, if the efficiency of Sai is 60% more than that of Priya ?

A) 8 days B) 12 days
C) 14 days D) 10 days
 
Answer & Explanation Answer: D) 10 days

Explanation:

Ratio of efficiencies of Priya and Sai is

Sai : Priya = 160 : 100 = 8 : 5

Given Priya completes the work in 16 days

Let number of days Sai completes the work be 'd'

=> 5×16 = 8×d

d = 10 days.

Therefore, number of days Sai completes the work is 10 days.

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13 5256
Q:

Pavan and Sravan are two persons. If Pavan works with his actual efficiency and Sravan twice of his actual efficiency then it takes 25 days to complete the work. But If Pavan works twice of his actual efficiency and Sravan with his normal efficiency then the work is completed in 20 days. How many days would it take if Sravan alone works with his actual efficiency (in Days)?

A) 50 B) 100
C) 70 D) 35
 
Answer & Explanation Answer: B) 100

Explanation:

Let the Efficiency of pavan be E(P)

Let the Efficiency of sravan be E(S)

Here Work W = LCM(25,20) = 100

Now, E(P+2S) = 100/25 = 4 ....(1)

E(2P+S) = 100/20 = 5 ....(2)

Hence, from (1) & (2) we get

E(S) = 1

=> Number of days Savan alone work to complete the work  = 100/1 = 100 days.

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10 5210
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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4 5180
Q:

A work which could be finished in 11 days was finished 4 days earlier after 4 more men joined. The number of men employed was ?

A) 7 B) 8
C) 9 D) 10
 
Answer & Explanation Answer: A) 7

Explanation:

As the work is same
M1D1 = M2D2

Here Let the number of men employed was M
=> 11M = 7(M+4)
=> 11M - 7M = 28
=> M = 7

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4 5155
Q:

Meghana alone would take 32 hours more to complete a job than both Meghana and Ganesh together. If Ganesh worked alone, he took 12 1/2 hours more to complete it than both Meghana and Ganesh worked together. What time would they take if both Meghana and Ganesh worked together?

A) 20 hrs B) 18 hrs
C) 22 hrs D) 20.5 hrs
 
Answer & Explanation Answer: A) 20 hrs

Explanation:

Time taken by both Meghana and Ganesh to work together is given by =

t1 x t2 

Where

t1 = 32 hrst2 = 12 12 hrs = 252 hrs

 

Therefore, time took by both to work together = 

32 x 252 = 16 x 25 = 4 x 5 = 20 hrs

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