GMAT Changed on April 16th - Read about the latest changes here

 It is currently 22 Apr 2018, 01:39

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Cape Cod Cookies makes cookies of identical size from batches of cooki

Author Message
TAGS:

### Hide Tags

Board of Directors
Joined: 01 Sep 2010
Posts: 3414

### Show Tags

04 Apr 2018, 16:20
Top Contributor
00:00

Difficulty:

15% (low)

Question Stats:

95% (02:11) correct 5% (02:47) wrong based on 38 sessions

### HideShow timer Statistics

Cape Cod Cookies makes cookies of identical size from batches of cookie dough weighing 600 ounces. Cape Cod Cookies decides to modify the recipe by decreasing the weight of each cookie by 1 ounce. If Cape Cod Cookies discovers that it is now able to make 30 more cookies using the same batch of dough weighing 600 ounces, how much did each cookie originally weigh?

A. 2

B. 3

C. 4

D. 5

E. 6

Kudos for the right answer and explanation
[Reveal] Spoiler: OA

_________________
SC Moderator
Joined: 13 Apr 2015
Posts: 1618
Location: India
Concentration: Strategy, General Management
WE: Analyst (Retail)

### Show Tags

04 Apr 2018, 18:29
1
KUDOS
$$\frac{600}{(x - 1)} - \frac{600}{x} = 30$$

Substitute the options for x, only option D satisfies.

Intern
Joined: 24 Mar 2018
Posts: 25

### Show Tags

04 Apr 2018, 21:36
1
KUDOS
Let's assume initially there were x cookies each weighing y ounce
As per the question,
x*y=600
(x+30)*(y-1)=600

On solving it we get y=5, which is the required solution.
Math Expert
Joined: 02 Aug 2009
Posts: 5774

### Show Tags

04 Apr 2018, 22:01
1
KUDOS
Expert's post
carcass wrote:
Cape Cod Cookies makes cookies of identical size from batches of cookie dough weighing 600 ounces. Cape Cod Cookies decides to modify the recipe by decreasing the weight of each cookie by 1 ounce. If Cape Cod Cookies discovers that it is now able to make 30 more cookies using the same batch of dough weighing 600 ounces, how much did each cookie originally weigh?

A. 2

B. 3

C. 4

D. 5

E. 6

Kudos for the right answer and explanation

As shown above too the correct equation is $$\frac{600}{n-1}-\frac{600}{n}=30$$..

EITHER solve it
$$\frac{600}{n-1}-\frac{600}{n}=30...........\frac{20}{n-1}-\frac{20}{n}=1.........20n-20n-20*(-1)=n(n-1)........n(n-1) = 20=5*4.$$..
OR
what you can see is the division by TWO consecutive integers and their difference 30 is multiple of 3..
so either both n and n-1 are MULTIPLE of 3 or both are NOT..
since they are consecutive, both together cannot be multiple of 3, so both will not be multiple of 3..

Only possibility is n and n-1 are 5 and 4..
D
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

GMAT online Tutor

Manager
Joined: 05 Feb 2016
Posts: 107
Location: India
Concentration: General Management, Marketing
WE: Information Technology (Computer Software)

### Show Tags

04 Apr 2018, 22:02
carcass wrote:
Cape Cod Cookies makes cookies of identical size from batches of cookie dough weighing 600 ounces. Cape Cod Cookies decides to modify the recipe by decreasing the weight of each cookie by 1 ounce. If Cape Cod Cookies discovers that it is now able to make 30 more cookies using the same batch of dough weighing 600 ounces, how much did each cookie originally weigh?

A. 2

B. 3

C. 4

D. 5

E. 6

Kudos for the right answer and explanation

substituting 1 in 2 we get.
600/(x-1)-600/x=30

checking from options

D satisfy..
Target Test Prep Representative
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2273

### Show Tags

10 Apr 2018, 11:14
carcass wrote:
Cape Cod Cookies makes cookies of identical size from batches of cookie dough weighing 600 ounces. Cape Cod Cookies decides to modify the recipe by decreasing the weight of each cookie by 1 ounce. If Cape Cod Cookies discovers that it is now able to make 30 more cookies using the same batch of dough weighing 600 ounces, how much did each cookie originally weigh?

A. 2

B. 3

C. 4

D. 5

E. 6

We can let w = original weight of each cookie in ounces and c = the original number of cookies. Thus we have:

wc = 600

When the weight of each cookie is reduced by 1 ounce, the number of cookies is increased by 30, so we have:

(w - 1)(c + 30) = 600

Expanding the second equation we have:

wc + 30w - c - 30 = 600

Since wc = 600, we have:

600 + 30w - c - 30 = 600

30w - c - 30 = 0

Also since wc = 600, c = 600/w. So we have:

30w - 600/w - 30 = 0

Multiply the entire equation by w, we have:

30w^2 - 600 - 30w = 0

w^2 - w - 20 = 0

(w - 5)(w + 4) = 0

w = 5 or w = -4

Since w can’t be negative, w = 5.

_________________

Jeffery Miller

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: Cape Cod Cookies makes cookies of identical size from batches of cooki   [#permalink] 10 Apr 2018, 11:14
Display posts from previous: Sort by