If it takes 70 workers 3 hours to disassemble the exhibition rides at

Question

Tough and Tricky questions: Work/Rate Problems.

If it takes 70 workers 3 hours to disassemble the exhibition rides at a small amusement park, how many hours would it take 30 workers to do this same job?

A. 40/3
B. 11
C. 7
D. 7/3
E. 9/7

Kudos for a correct  solution .

Source: Chili Hot GMAT

manpreetsingh86 · Answer

let w= 210 units.
thus rate of each worker =  \frac{210}{3.70}  =  1   unit

hence, time taken by 30 workers to complete 210 units = \frac{210}{30}  =  7   days

intheend14 · Answer

Choice C

It takes 70 workers 3 hours to finish the task. This means we can set up the expression 70 * 1/x = 1/3 hours. Solving for x, yields 210 hours or the time it would take each worker on their own. So, for 3 workers, it takes 30*1/x = 1/T (hours). Since x=210 hours, we can solve for T to be 7 hours.

sunaimshadmani · Answer

70 Workers = 3 hours then, 
1 Worker = 3*70 Hours
30 Workers = (3*70) /(30) = 7 Answer.

amitshri15 · Answer

Work = worker * time = 70 * 3 =210.
210 = 30 * t => t =7.

Answer is C.

PareshGmat · Answer

Answer = C = 7

Rate of one worker  = \frac{1}{70*3} = \frac{1}{210}

Rate of 30 workers  = 30 * \frac{1}{210} = \frac{1}{7}

Time taken = 7 Hours

Bunuel · Answer

Yes, the correct answer is C.

GMATinsight · Answer

CONCEPT :  \frac{(Machine_Power * Time)}{Work} = Constant   
i.e.  \frac{(M_1 * T_1)}{W_1} = \frac{(M_2 * T_2)}{W_2}

i.e.  \frac{(70 * 3)}{1} = \frac{(30 * T_2)}{1}

i.e.  T_2 = 7

Answer: option C

gracie · Answer

t*30*1/210=1
t=7 hours

mdcf · Answer

Why does setting up a proportion lead you to the wrong answer?

(70 workers/3 hours) = (30 workers/X hours)

pushpitkc · Answer

Hi  mdcf

70 workers take 3 hours - Work done is 210 worker hours
30 workers take X hours - Work done is 30X worker hours

Here, we can equate the work done by 70 machines and 30 machines, 30X = 210 
Solving for X, we get X =  \frac{210}{30} = 7

What you were trying to equate was the work done in an hour(which is not the same)

Hope this helps you!

ScottTargetTestPrep · Answer

The rate of 70 workers is 1/3;if we let x = the rate of 30 workers, then we can set up the proportion

70/(1/3) = 30/x

70x = 30(1/3)

70x = 10

x = 1/7

Since the rate of the 30 workers is 1/7, the time it takes to do the job is 1/(1/7) = 7 hours.

Answer: C

GyMrAT · Answer

The job requires 70 * 3 = 210 man hours

Hence 30 workers will finish the job in = 210/30 = 7 hours.

Answer C.

Thanks,
GyM

EgmatQuantExpert · Answer

Solution

Given:

• 70 workers take 3 hours to disassemble the exhibition rides.

To find:

• How many hours will 30 workers take to disassemble the exhibition rides.

Approach and Working:

70 workers take 3 hours to disassemble the exhibition rides.
 • Thus, complete work takes 70*3= 210 worker-hours to complete the work.

Now, if 30 workers do the same work then,
 • They will take 210/30= 7 hours to do the same work.

Hence, the correct answer is option C.

Answer: C

Kinshook · Answer

Asked: If it takes 70 workers 3 hours to disassemble the exhibition rides at a small amusement park, how many hours would it take 30 workers to do this same job?

Worker-hours = 70 * 3 = 30*x 
x = 7

IMO C

If it takes 70 workers 3 hours to disassemble the exhibition rides at

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If it takes 70 workers 3 hours to disassemble the exhibition rides at

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