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:

S, T and U together can complete a work in 30 days. If the ratio of efficiency of S, T and U is 20 : 15 : 12 respectively, then in how many days U alone can complete the same work?

A) 195/2 B) 235/2
C) 225/2 D) 215/2
 
Answer & Explanation Answer: B) 235/2

Explanation:
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7 1397
Q:

Lasya alone can do a work in 16 days. Srimukhi’s efficiency is 20 % lesser than that of Laya. If Rashmi and Srimukhi together can do the same work in 12 days, then find the efficiency ratio of Rashmi to that of Lasya?

A) 19 : 7 B) 30 : 19
C) 8 : 15 D) 31 : 17
 
Answer & Explanation Answer: C) 8 : 15

Explanation:

Given Lasya can do a work in 16 days.

 

Now, time taken by Srimukhi alone to complete the work = 16 x 100/80

 

Time taken by Rashmi = n days

 

=> (12 x 20)/(20 - 12) = (12 x 20)/n

 

=> n= 30 days.

 

Required ratio of efficiencies of Rashmi and Lasya = 1/30  ::  1/16  = 8 : 15.

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7 3284
Q:

A and B can together complete a task in 18 hours. After 6 hours A leaves. B takes 36 hours to finish rest of the task. How many hours would A have taken to do the task if he worked alone?

A) 54 B) 45
C) 21 D) 27
 
Answer & Explanation Answer: D) 27

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7 1179
Q:

A certain job was assigned to a group of women to do it in 20 days. But 12 women did not turn up for the job and the remaining did the job in 32 days. The original number of women in the group was?

A) 36 B) 32
C) 22 D) 28
 
Answer & Explanation Answer: B) 32

Explanation:

Let the total women in the group be 'W'

Then according to the given data,

 W x 20 = (W-12) x 32

 => W = 32 

Therefore, the total number of women in the group = 32

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7 5478
Q:

One girl can eat 112 chocolates in half a minute, and her boy friend can eat half as many in twice the length of time. How many chocolates can both boy and girl eat in 12 seconds ?

A) 44 B) 32
C) 56 D) 49
 
Answer & Explanation Answer: C) 56

Explanation:

Girl eats 112 chocolates in 30 sec

so she can eat in 12 sec is 12 x 112/30 = 44.8 chocolates.

 

Her boy friend can eat one-half of 112 in twice of 30 sec

so he can eat 56 in 60 sec


Then he can eat in 12 sec is 56 x 12/60 = 11.2 chocolates.

 

Hence, together they can eat = 44.8 + 11.2 =56 chocolates in 12 seconds.

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7 2857
Q:

A and B have to type a book together containing 120 pages. A takes 9 hrs to type 36 pages and B takes 5 hrs to type 40 pages. A typed first 60 pages alone and the last 60 pages were typed by A and B together. How much time (in hours) will be taken to type the complete book?

A) 24 B) 20
C) 12 D) 15
 
Answer & Explanation Answer: B) 20

Explanation:
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7 1364
Q:

A, B and C can do a piece of work in 72, 48 and 36 days respectively. For first p/2 days, A & B work together and for next ((p+6))/3days all three worked together. Remaining 125/3% of work is completed by D in 10 days. If C & D worked together for p day then, what portion of work will be remained?

A) 1/5 B) 1/6
C) 1/7 D) 1/8
 
Answer & Explanation Answer: B) 1/6

Explanation:

Total work is given by L.C.M of 72, 48, 36

Total work = 144 units

Efficieny of A = 144/72 = 2 units/day

Efficieny of B = 144/48 = 3 units/day

Efficieny of C = 144/36 = 4 units/day

 

According to the given data,

2 x p/2 + 3 x p/2 + 2 x (p+6)/3 + 3 x (p+6)/3 + 4 x (p+6)/3 = 144 x (100 - 125/3) x 1/100

3p + 4.5p + 2p + 3p + 4p = 84 x 3 - 54

p = 198/16.5

p = 12 days.

 

Now, efficency of D = (144 x 125/3 x 1/100)/10 = 6 unit/day

(C+D) in p days = (4 + 6) x 12 = 120 unit

Remained part of work = (144-120)/144 = 1/6.

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7 5830
Q:

Mr. stenley employed a certain number of typist for his project. 8 days later 20% of the typist left the job and it was found that it took as much time to complete the rest work from then as the entire work needed with all the employed typists. The average speed of a typist is 20 pages/hour. Minimum how many typist could be employed? 

A) 10 B) 5
C) 15 D) 4
 
Answer & Explanation Answer: B) 5

Explanation:

Since 20% i.e 1/5 typists left the job. So, there can be any value which is multiple of 5 i.e, whose 20% is always an integer. Hence, 5 is the least possible value.

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