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# M24 Q 24

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VP
Joined: 05 Jul 2008
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12 Mar 2009, 14:54
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In normal printing mode, 20 printers can print 100 pages in 3 minutes. In economy mode, printers work 20% faster than in normal mode. How many printers are required to print 180 pages in 3 minutes in economy mode?

(A) 25
(B) 28
(C) 29
(D) 30
(E) 32

[Reveal] Spoiler: OA
D

Source: GMAT Club Tests - hardest GMAT Questions

I pulled this off but I want to hear from folks on their approaches

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SVP
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12 Mar 2009, 18:55
2
KUDOS
icandy wrote:
I pulled this off but I want to hear from folks on their approaches

In normal printing mode, 20 printers can print 100 pages in 3 minutes. In economy mode, printers work 20% faster than in normal mode. How many printers are required to print 180 pages in 3 minutes in economy mode?

(C) 2008 GMAT Club - m24#24

* 25
* 28
* 29
* 30
* 32

normal mod = 100/20*3 = 5/3 PAGES/printer/minute

economy mode printer rate = 5/3 *1.2 = 2 pages/printer/minute

priner rate for 3 minutes = 6 pages/printer = 180 pages /30 printers

30

D
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Manager
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16 Mar 2009, 09:46
1
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icandy wrote:
I pulled this off but I want to hear from folks on their approaches

In normal printing mode, 20 printers can print 100 pages in 3 minutes. In economy mode, printers work 20% faster than in normal mode. How many printers are required to print 180 pages in 3 minutes in economy mode?

(C) 2008 GMAT Club - m24#24

* 25
* 28
* 29
* 30
* 32

Method:

1) First find out the time required to print 1 page in 3 Minutes (here 3 Minutes because answer ask for the same) with 1 printer and you will find one printer prints 6 pages in 3 minutes after their percentage increase in economical speed.

(100 / 20) * (120 / 100) = 6 pages.

2) Once you find this it is easy to find for 180 pages how many printer requires. (30).

2) Once you find 6

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Intern
Joined: 06 Mar 2009
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20 Mar 2009, 13:18
In economy mode printers print 20% faster. Hence 20 printers will print 120 pages in 3 mins. You want 1.5 times of 120 pages, hence you multiply 1.5 * 20 printers (and don't touch the time at all, as we want to find out the number of pages in 3 mins) = 30 printers.

Hence, ANS - 30 printers

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Director
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Name: Ronak Amin
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05 Apr 2009, 03:14
1
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Normal mode rate = 100/(3*20)
Economy mode rate = 1.20 * 100/(3*20)

Now, let x be the number of economy mode printers.
Adding rates of all printers = Combined rate of printers

x * 1.20 * 100/(3*20) = 180/3
=>x = 30

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Manager
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10 Apr 2009, 00:29
20 printer, 100 page, 3 minutes
1 printer, 5 page, 3 minutes
in economy it is 20% faster
so,
1 printer, 5+1 page , 3 minutes
30 printer, 180 page, 3 minutes.
icandy wrote:
I pulled this off but I want to hear from folks on their approaches

In normal printing mode, 20 printers can print 100 pages in 3 minutes. In economy mode, printers work 20% faster than in normal mode. How many printers are required to print 180 pages in 3 minutes in economy mode?

(C) 2008 GMAT Club - m24#24

* 25
* 28
* 29
* 30
* 32

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Intern
Joined: 26 Jul 2010
Posts: 24

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08 Dec 2010, 10:21
100 pages in 3 minutes. 20% more in Econ mode means 120 pages in 3 minutes, 20 printers. So, for 180 pages, 3 minutes, it would take 30 printers. So answer is (D)

Posted from my mobile device

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Intern
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08 Dec 2010, 10:49
20 printer, 100 page
1 printer, 5 page
in economy it is 20% faster
so,
1 printer, 5+1 page
==> 180 /6 = 30 printers

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Manager
Status: I rest, I rust.
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09 Dec 2010, 01:04
icandy wrote:
In normal printing mode, 20 printers can print 100 pages in 3 minutes. In economy mode, printers work 20% faster than in normal mode. How many printers are required to print 180 pages in 3 minutes in economy mode?

(A) 25
(B) 28
(C) 29
(D) 30
(E) 32

Normal Printing Mode:
20 Printers, 100 pages, 3 minutes means 1 Printer, 1 Page, $$\frac{20*3}{100}$$ min.

Economy Mode:
1 Printer, 1 page, $$\frac{80}{100}*\frac{60}{100}$$ min.
1 Printer, 180 Pages, $$\frac{180*8*6}{100}$$ min.

If printing must be finished in 3 minutes, number of printers required= $$\frac{18*8*6}{10}*\frac{1}{3} = 28.8$$.
Rounding it nearest integer, 29.

Why is that wrong??
Shouldnt "20% Faster" mean "same number of pages in 80% of the time", and not "20% more pages in same duration"??
_________________

Respect,
Vaibhav

PS: Correct me if I am wrong.

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Intern
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09 Dec 2010, 13:06
I have the same thoughts as vaibhavtripathi.

Doesn't faster mean less time and not more pages?

Thanks

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Intern
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13 Dec 2010, 02:44
Normal:20 Printers 100Pages 3 min=> 20:100:3
Eco: 20Printers 100Pages+20%100pages 3 mins=>20:120:3
120/20=6pages per printer
so 180 pages need to print means =>180/6 = 30 printer

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Manager
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12 Dec 2011, 07:10
D.

I had to read the question twice to solve it the simplest way. The 3 mins remains constant which test takers need to identify immediately after reading the que to solve it accurately and quickly.
After looking at the explanation it looks easy. But on the real GMAT we may not solve this in 2 mins if you do not read and understand the question clearly. Good question with multiple variables.

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Manager
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18 Feb 2012, 14:50
D.

we get 1 printer = 5 pages / 3 min
i used a little estimation and got ~ 2 per page with the 120%

[2p x 3 minute]=180 or 30 printers.

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Math Expert
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12 Dec 2012, 06:09
6
KUDOS
Expert's post
In normal printing mode, 20 printers can print 100 pages in 3 minutes. In economy mode, printers work 20% faster than in normal mode. How many printers are required to print 180 pages in 3 minutes in economy mode?

A. 25
B. 28
C. 29
D. 30
E. 32

In normal printing mode, 1 printer can print 100/20=5 pages in 3 minutes.
In economy mode, 1 printer can print 5*1.2=6 pages in 3 minutes.

So, to print 180 pages in 3 minutes in economy mode 180/6=30 printers are needed.

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Intern
Status: Preparing for GMAT
Joined: 19 Sep 2012
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Location: India
GMAT Date: 01-31-2013
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12 Dec 2012, 06:35
2
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20 Printers = 3 mins = 120 pages (economy mode) =given ..so
10 Printers = 3 mins = 60 pages..

hence

30 Printer = 3mins = 180 pages.. (just mental calucation reuqired)
_________________

Rajeev Nambyar
Chennai, India.

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Manager
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12 Dec 2012, 09:35
2
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Since both the Q and Answer is computed for 3 mins, time can be saved not to include 3 in computations.

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Intern
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12 Dec 2012, 11:24
D was able to pull this off just under 2mins looks like a simple one
Normal mode:per printer per min = 100/(3*20)=5/3
Eco mode is 20% faster than normal mode would mean it can print 1.2 times 5/3= (12/10)*(5/3) = 2pages per min
Total time 3 mins , in eco mode we get 6 pages in 3 min( 2*3)
No. of printer required for 180 pages in 3 mins can be derived by 180/6 = 30 and that is the answer = D

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Manager
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12 Dec 2012, 12:04
D...pretty easy one....solved in head...didnt even wrote it down...:)

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Intern
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13 Dec 2012, 12:18
Straightaway D.
This is the hardest? Are you kidding me?
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Manager
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06 Dec 2013, 20:17
Very easy question...

Firstly calculate for the 150 pages in normal mode...because 150(Normal) + 20% of 150(Normal) = 180(Economy)

Normal - 20 printers - 100 pages in 3 minutes
Normal - 30 printers - 150 pages in 3 minutes
Economy - 30 printers - 180 pages in 3 minutes

So, D.
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Re: M24 Q 24   [#permalink] 06 Dec 2013, 20:17
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# M24 Q 24

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