420+ Solved Time and Work Problems with Solutions and Explanation

Q:

In a computer game, there are builders and destroyers. Together there are 20 of them. Some of them try to build a wall around a castle while the rest try to demolish it. Each of the builders can build the wall alone in 15 hours while any of the destroyers can demolish it in 10 hours. If all 20 builders and destroyers are made active when there is no wall and the wall gets built in 3 hours, how many of them are destroyers?

A) 5	B) 7
C) 6	D) 8

Answer & Explanation Answer: C) 6

Explanation:

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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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Q:

5 men and 3 boys can together cultivate a 23 acre field in 4 days and 3 men and 2 boys together can cultivate a 7 acre field in 2 days. How many boys will be needed together with 7 men, if they cultivate 45 acre of field in 6 days.

A) 6	B) 4
C) 2	D) 3

Answer & Explanation Answer: C) 2

Explanation:

Let work done by 1 man in i day be m

and Let work done by 1 boy in 1 day be b

From the given data,

4(5m + 3b) = 23

20m + 12b = 23....(1)

2(3m + 2b) = 7

6m + 4b = 7 ....(2)

By solving (1) & (2), we get

m = 1, b = 1/4

Let the number of required boys = n

6(7 1 + n x 1/4) = 45

=> n = 2.

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Q:

A does 75% of a work in 50 days. He then calls in B and they together finish the remaining work in 10 days. How long B alone would take to complete the whole work?

A) 200 days	B) 50 days
C) 100 days	D) 125 days

Answer & Explanation Answer: C) 100 days

Explanation:

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Q:

Prabhas is twice as good a workman as Rana and finishes a piece of work in 3 hours. In how many hours they together could finish that piece of work?

A) 3 hrs	B) 3.5 hrs
C) 2.5 hrs	D) 2 hrs

Answer & Explanation Answer: D) 2 hrs

Explanation:

Given Prabhas is twice as good a workman as Rana.

Prabhas finishes the work in 3 hrs

=> Rana finishes the work in 6 hrs.

Number of hours required together they could finish the work

= 3 x 6 / 3 + 6

= 18/9

= 2 hrs.

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Q:

A can finish a work in 18 days and B in 36 days. If they work on it together for 9 days, then what percent of work is left?

A) 33.3	B) 20
C) 75	D) 25

Answer & Explanation Answer: D) 25

Explanation:

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Q:

A & B together finish a job in 24 days, while A, B & C together can finish the same job in 8 days. C alone will finish the job in

A) 12 days	B) 14 days
C) 16 days	D) 24 days

Answer & Explanation Answer: A) 12 days

Explanation:

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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) $3 \frac{4}{49} d a y s$

B) $12 \frac{4}{49} d a y s$

C) $4 \frac{3}{49} d a y s$

D) $4 \frac{12}{49} d a y s$

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 = $(\frac{1}{108} + \frac{1}{88}) = \frac{49}{2376}$

So, both Raghu and Arun will finish the work in $\frac{2376}{49} h r s$

Number of days of 12 hours each= $(\frac{2376}{49} \times \frac{1}{12})$ = $\frac{198}{49} = 4 \frac{3}{49} d a y s$

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