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A candy manufacturer decided to decrease the weight of each candy bar,

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A candy manufacturer decided to decrease the weight of each candy bar, [#permalink]

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New post 29 Jan 2016, 03:21
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A
B
C
D
E

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64% (01:14) correct 36% (01:27) wrong based on 135 sessions

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A candy manufacturer decided to decrease the weight of each candy bar, while retaining the price. By how many cents did the per kilogram cost of candy change after the reduction in weight?

(1) The weight of each piece of candy bar reduced by 9 grams.
(2) The weight of each piece of candy bar reduced by 9%

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Re: A candy manufacturer decided to decrease the weight of each candy bar, [#permalink]

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New post 29 Jan 2016, 08:55
Let each candybar weigh x grams, and cost D dollars. Then, cost of candybars per kilogram would be (1000/x)*D. If the new weight of each candybar is y, we are asked to determine [(1000/y)-(1000/x)]*D = 1000D[(1/y)-(1/x)]

(1) y = x-9 => Cost difference = 1000D[(1/(x-9))-(1/x)]; Insufficient.
(2) y = 0.91x => Cost difference = 1000D[(1/(0.91x)-(1/x)]; Insufficient.

(1) + (2) => x = 100, y = 91 => Cost difference = 1000D[(1/(91)-(1/100)]; Insufficient.

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Re: A candy manufacturer decided to decrease the weight of each candy bar, [#permalink]

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New post 29 Jan 2016, 21:24
The answer should be E.As we have to find change in price per kilogram,we need to know the price of candy.option A&B are pertaining to weight alone.
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Re: A candy manufacturer decided to decrease the weight of each candy bar, [#permalink]

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New post 30 Jan 2016, 10:25
Let us assume price of each candy piece be P
A)
Initial weight of Candy be X
price per kg = (1000/X )*P
After reduction= (1000/X-9) * P

Change in price per kg= ((100/X-9)*P-(1000/X)*P)/((1000/X )*P)
= 900/X-9
Insufficient
B.
Weight after reduction = .91X

Price change = [(1000/0.91X)*P)- ((1000/X)*P) ]/ ((1000/P )*X)
= 900/91
So B is sufficient
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Re: A candy manufacturer decided to decrease the weight of each candy bar, [#permalink]

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New post 30 Jan 2016, 11:13
kanigmat011

I have a question

(1000/0.91X)*P)= New price per kg
(1000/X)*P = Old price per kg

(1000/0.91X)*P)-(1000/X)*P= change in price per kg.This is what we have to find out.

Then why you are dividing it by """((1000/P )*X)"""
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Re: A candy manufacturer decided to decrease the weight of each candy bar, [#permalink]

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New post 30 Jan 2016, 11:26
pkm9995109794 wrote:
kanigmat011

I have a question

(1000/0.91X)*P)= New price per kg
(1000/X)*P = Old price per kg

(1000/0.91X)*P)-(1000/X)*P= change in price per kg.This is what we have to find out.

Then why you are dividing it by """((1000/P )*X)"""



Hey PKM,

Thanks for pointing out my mistake
Indeed Option E is correct

Misunderstood the question stem!
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Re: A candy manufacturer decided to decrease the weight of each candy bar, [#permalink]

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New post 30 Jan 2016, 22:47
Hi Folks!
IMO it should be..
most important logic what I used here to save time: if there was percentage increase or decrease was asked then needed to go in depth to solve...
so here we are asked in absolute terms in dollars or cents... and in none of the options we are given any info about the dollar or cents increase or decrease..
So it should be E.

Kudos please if its a correct solution.

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Re: A candy manufacturer decided to decrease the weight of each candy bar, [#permalink]

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New post 30 Jan 2016, 23:08
1
Bunuel wrote:
A candy manufacturer decided to decrease the weight of each candy bar, while retaining the price. By how many cents did the per kilogram cost of candy change after the reduction in weight?

(1) The weight of each piece of candy bar reduced by 9 grams.
(2) The weight of each piece of candy bar reduced by 9%



Hi,

As always I would first look into the Q STEM and see what is required for answer and then check statements if that info is being provided by the statements..

INFO FROM Q...
THe price remains the same , while the weight is reduced.
WE are to find-- By how many cents did the per kilogram cost of candy change after the reduction in weight?..

What is required to answer?
the price for some Qty..
the reduction in weight..
or some ratio which involves price somewhere..

lets see the statements..
(1) The weight of each piece of candy bar reduced by 9 grams.
Talks of only weight part, nothing about price...
insuff

(2) The weight of each piece of candy bar reduced by 9%
gives the weight reduction in % , again nothing on price..
Insuff..

Combined..
we can just say that the weight of each candy was 100gms and reduced to 91 later..
nothing about price..
insuff
E
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Re: A candy manufacturer decided to decrease the weight of each candy bar, [#permalink]

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New post 31 Jan 2016, 22:07
1
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

A candy manufacturer decided to decrease the weight of each candy bar, while retaining the price. By how many cents did the per kilogram cost of candy change after the reduction in weight?

(1) The weight of each piece of candy bar reduced by 9 grams.
(2) The weight of each piece of candy bar reduced by 9%

When you modify the original condition and the question, this question is frequently given on GMAT Math, which is “2 by 2” question.

Attachment:
BGDS   Bunuel    A candy manufacturer decided (20160131).jpg
BGDS Bunuel A candy manufacturer decided (20160131).jpg [ 23.88 KiB | Viewed 1057 times ]

On the table, there are 3 variables(p,a,b), which should match with the number of equations. So you need 3 equations. For 1) 1 equation, for 2) 1 equation, which is likely to make E the answer. When 1) & 2), b=100, a=91, but you cannot figure out the price and can’t get the answer in a unique way. It is not sufficient.
Therefore, the answer is E.


 For cases where we need 3 more equations, such as original conditions with “3 variables”, or “4 variables and 1 equation”, or “5 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 80% chance that E is the answer (especially about 90% of 2 by 2 questions where there are more than 3 variables), while C has 15% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since E is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, C or D.
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Re: A candy manufacturer decided to decrease the weight of each candy bar, [#permalink]

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New post 20 Apr 2017, 10:48
A is insufficient because we don't know about price. B is insufficient as we know the percentage change but not actual values of price and weight. Say original weight is x grams and price is y cents. With B, weight is 0.91x but we don't have values of x and y. When combined, I know 9/100x = 9 grams, so I get value of x, yet no value of y. Hence, insufficient. Answer is E
Re: A candy manufacturer decided to decrease the weight of each candy bar,   [#permalink] 20 Apr 2017, 10:48
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A candy manufacturer decided to decrease the weight of each candy bar,

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