It takes 50 identical printing presses 8 hours to print 500,000 papers

Question

It takes 50 identical printing presses 8 hours to print 500,000 papers. How long would it take 40 of these presses to print the same total?

A. 9 hr, 36 min
B. 10 hr
C. 12 hr 24 min
D. 12 hr, 40 min
E. 13 hr, 20 min

Kudos for a correct  solution .

chetan2u · Answer

since the number of papers is the same , we require to find the relation in number of presses and time taken..
50 takes 8 hrs..
1 will take 50*8 hrs..
40 will take 50*8/40=10hrs
ans B

ENGRTOMBA2018 · Answer

total work needed = 500,000*50*8

total work supplied = 500,000*40*x

As total work should be the same ---> 500,000*50*8 = 500,000*40*x ---> x = 10 hours. B is the correct answer.

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{(50 * 8)}{500000} = \frac{(40 * T_2)}{500000}

i.e.  T_2 = 10

Answer: option B

TimeTraveller · Answer

No. of papers to print =  500,000 * 50 * 8

Time taken =  \frac{500,000 * 50 * 8}{500,000 * 40} = \frac{400}{40} = 10 . Ans (B).

chetan2u · Answer

Re: It takes 50 identical printing presses 8 hours to print 500,000 papers   New post Jul 21, 2015 10:25 pm
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Bunuel wrote:
It takes 50 identical printing presses 8 hours to print 500,000 papers. How long would it take 40 of these presses to print the same total?

A. 9 hr, 36 min
B. 10 hr
C. 12 hr 24 min
D. 12 hr, 40 min
E. 13 hr, 20 min

Kudos for a correct solution.

50 machines finish the job in 8 hours. We do not have to take care of the 500'000 papers, it does not matter. 
40 machines means, 20% less of capacity and therefore 20% longer to work for a certain job.

8 * 1.2 = 9 hr, 36 min

Answer A ..
Hi reto,
since you are looking time for 40 presses it is 25% less so will take 25% more ..
ans 8*1.25=10 hrs..

reto · Answer

Thanks  chetan2u

I erased my posted, was a bit embarrassing. I don't understand the logic, if you discount from 50 to 40 it is 20%. Why is it that you have to compare 50/40 = Factor 1.25. It is not logical for me.

ENGRTOMBA2018 · Answer

reto , do not delete your posts as you always learn from your mistakes/gaps in reasoning.

As for your question, you are calculating % wrt 50 and getting 20% while you should actually be looking for % wrt 40 (=10/40= 25%). This is because you need wrt 40 and not wrt 50.

Hope this helps.

KS15 · Answer

Using chain rule,

(50 presses* 8hours)/500,000 papers=(40 presses*x hours)/500,000 papers
Answer 10 hours
B

Bunuel · Answer

800score Official Solution:

If it takes 50 presses 8 hours to print 500,000 papers, then it takes 50 × 8 = 400 press-hours to make the total. If there were only 40 presses, and 400 press-hours were needed to print the papers, then each press would need to work for 400/40 = 10 hours to finish the total.

The correct answer is choice (B).

Mathivanan Palraj · Answer

Since the number of papers in both the cases are same we need not consider that part.
50 presses complete a task in 8 hours, therefore 40 presses can complete in 8*50/40 = 10 hours.

bumpbot · Answer

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It takes 50 identical printing presses 8 hours to print 500,000 papers

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It takes 50 identical printing presses 8 hours to print 500,000 papers

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