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Each member of a pack of 55 wolves has either brown or blue [#permalink]

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23 Oct 2011, 09:23

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Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves?

(1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1.

Not able to understand the line " If there are more than 3 blue-eyed wolves with white coats"

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves?

Look at the matrix below:

"There are more than 3 blue-eyed wolves with white coats" means that # of wolves which have blue eyes AND white coats is more than 3. The question asks whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

(1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. Not sufficient on its own. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1. Not sufficient on its own.

(1)+(2) When taken together we get the flowing matrix:

Notice that x and y must be integers (they represent some positive multiples for the ratios given in the statements).

So, we have that 3y+7x=55. After some trial and error we can find that this equation has only 3 positive integers solutions: y=2 and x=7 --> 3y+7x=6+49=55; y=9 and x=4 --> 3y+7x=27+28=55; y=16 and x=1 --> 3y+7x=48+7=55;

Now, the third solution (x=1) is not valid, since in this case # of wolves which have blue eyes AND white coats becomes 3x=3, so not more than 3 as given in the stem. As for the first two cases, in both of them 7x is more than 3y (49>6 and 28>27), so we can answer definite YES, to the question whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

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.

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves?

(1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1.

Transforming the original condition and the question, we have the below 2by2 question which is a typical question in GMAT test.

There are 4 variables (a,b,c,d), 2 equations (a+b+c+d=55, b>3) and we need 2 more equations to match the number of variables and equations. Since there is 1 each in 1) and 2), there is high probability that C is the answer, and it actually turns out that C is the answer.

Attachments

GC DS LalaB Each member of a pack of (20150913).png [ 3.07 KiB | Viewed 2003 times ]

Re: Each member of a pack of 55 wolves has either brown or blue [#permalink]

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17 Mar 2012, 02:43

LalaB wrote:

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves? (1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1.

Not able to understand the line " If there are more than 3 blue-eyed wolves with white coats"
_________________

Re: Each member of a pack of 55 wolves has either brown or blue [#permalink]

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17 Mar 2012, 09:13

Bunuel wrote:

shadabkhaniet wrote:

Not able to understand the line " If there are more than 3 blue-eyed wolves with white coats"

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves?

Look at the matrix below:

Attachment:

Wolves.png

"There are more than 3 blue-eyed wolves with white coats" means that # of wolves which have blue eyes AND white coats is more than 3. The question asks whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

(1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. Not sufficient on its own. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1. Not sufficient on its own.

(1)+(2) When taken together we get the flowing matrix:

Attachment:

Wolves (1)+(2).png

Notice that x and y must be integers (they represent some positive multiples for the ratios given in the statements).

So, we have that 3y+7x=55. After some trial and error we can find that this equation has only 3 positive integers solutions: y=2 and x=7 --> 3y+7x=6+49=55; y=9 and x=4 --> 3y+7x=27+28=55; y=16 and x=1 --> 3y+7x=48+7=55;

Now, the third solution (x=1) is not valid, since in this case # of wolves which have blue eyes AND white coats becomes 3x=3, so not more than 3 as given in the stem. As for the first two cases, in both of them 7x is more than 3y (49>6 and 28>27), so we can answer definite YES, to the question whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

Re: Each member of a pack of 55 wolves has either brown or blue [#permalink]

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21 Aug 2013, 02:46

Bunuel wrote:

shadabkhaniet wrote:

Not able to understand the line " If there are more than 3 blue-eyed wolves with white coats"

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves?

Look at the matrix below:

Attachment:

Wolves.png

"There are more than 3 blue-eyed wolves with white coats" means that # of wolves which have blue eyes AND white coats is more than 3. The question asks whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

(1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. Not sufficient on its own. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1. Not sufficient on its own.

(1)+(2) When taken together we get the flowing matrix:

Attachment:

Wolves (1)+(2).png

Notice that x and y must be integers (they represent some positive multiples for the ratios given in the statements).

So, we have that 3y+7x=55. After some trial and error we can find that this equation has only 3 positive integers solutions: y=2 and x=7 --> 3y+7x=6+49=55; y=9 and x=4 --> 3y+7x=27+28=55; y=16 and x=1 --> 3y+7x=48+7=55;

Now, the third solution (x=1) is not valid, since in this case # of wolves which have blue eyes AND white coats becomes 3x=3, so not more than 3 as given in the stem. As for the first two cases, in both of them 7x is more than 3y (49>6 and 28>27), so we can answer definite YES, to the question whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

Answer: C.

Hope it's clear.

There could be another solution to the equation: y=11 and x=3 --> 3y+7x=33+21=55; and in this case, 7x < 3y => A & B together are insufficient => E is the answer Am I missing something here?

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves?

Look at the matrix below:

Attachment:

Wolves.png

"There are more than 3 blue-eyed wolves with white coats" means that # of wolves which have blue eyes AND white coats is more than 3. The question asks whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

(1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. Not sufficient on its own. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1. Not sufficient on its own.

(1)+(2) When taken together we get the flowing matrix:

Attachment:

Wolves (1)+(2).png

Notice that x and y must be integers (they represent some positive multiples for the ratios given in the statements).

So, we have that 3y+7x=55. After some trial and error we can find that this equation has only 3 positive integers solutions: y=2 and x=7 --> 3y+7x=6+49=55; y=9 and x=4 --> 3y+7x=27+28=55; y=16 and x=1 --> 3y+7x=48+7=55;

Now, the third solution (x=1) is not valid, since in this case # of wolves which have blue eyes AND white coats becomes 3x=3, so not more than 3 as given in the stem. As for the first two cases, in both of them 7x is more than 3y (49>6 and 28>27), so we can answer definite YES, to the question whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

Answer: C.

Hope it's clear.

There could be another solution to the equation: y=11 and x=3 --> 3y+7x=33+21=55; and in this case, 7x < 3y => A & B together are insufficient => E is the answer Am I missing something here?

Each member of a pack of 55 wolves has either brown or blue eyes and e [#permalink]

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01 Sep 2014, 09:29

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves? (1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1.

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves? (1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1.

Merging topics.

Please refer to the discussion above.
_________________

Re: Each member of a pack of 55 wolves has either brown or blue [#permalink]

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12 Sep 2015, 08:50

Bunuel wrote:

shadabkhaniet wrote:

Not able to understand the line " If there are more than 3 blue-eyed wolves with white coats"

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves?

Look at the matrix below:

Attachment:

Wolves.png

"There are more than 3 blue-eyed wolves with white coats" means that # of wolves which have blue eyes AND white coats is more than 3. The question asks whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

(1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. Not sufficient on its own. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1. Not sufficient on its own.

(1)+(2) When taken together we get the flowing matrix:

Attachment:

Wolves (1)+(2).png

Notice that x and y must be integers (they represent some positive multiples for the ratios given in the statements).

So, we have that 3y+7x=55. After some trial and error we can find that this equation has only 3 positive integers solutions: y=2 and x=7 --> 3y+7x=6+49=55; y=9 and x=4 --> 3y+7x=27+28=55; y=16 and x=1 --> 3y+7x=48+7=55;

Now, the third solution (x=1) is not valid, since in this case # of wolves which have blue eyes AND white coats becomes 3x=3, so not more than 3 as given in the stem. As for the first two cases, in both of them 7x is more than 3y (49>6 and 28>27), so we can answer definite YES, to the question whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

Answer: C.

Hope it's clear.

Hello Bunel , why should i see x only as integer , why can't it be fraction with denominator as 7 eg:18/7 ?

Not able to understand the line " If there are more than 3 blue-eyed wolves with white coats"

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves?

Look at the matrix below:

Attachment:

Wolves.png

"There are more than 3 blue-eyed wolves with white coats" means that # of wolves which have blue eyes AND white coats is more than 3. The question asks whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

(1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. Not sufficient on its own. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1. Not sufficient on its own.

(1)+(2) When taken together we get the flowing matrix:

Attachment:

Wolves (1)+(2).png

Notice that x and y must be integers (they represent some positive multiples for the ratios given in the statements).

So, we have that 3y+7x=55. After some trial and error we can find that this equation has only 3 positive integers solutions: y=2 and x=7 --> 3y+7x=6+49=55; y=9 and x=4 --> 3y+7x=27+28=55; y=16 and x=1 --> 3y+7x=48+7=55;

Now, the third solution (x=1) is not valid, since in this case # of wolves which have blue eyes AND white coats becomes 3x=3, so not more than 3 as given in the stem. As for the first two cases, in both of them 7x is more than 3y (49>6 and 28>27), so we can answer definite YES, to the question whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

Answer: C.

Hope it's clear.

Hello Bunel , why should i see x only as integer , why can't it be fraction with denominator as 7 eg:18/7 ?

Because if x = fraction , lets say =18/7, then 3x = NUMBER OF WOLVES with white coats = 54/7 = fraction . How can number of wolves be fraction? It does not make any sense to say we have 3/4 wolves or 22/7 wolves etc. Thus, x can only take integer values.
_________________

Re: Each member of a pack of 55 wolves has either brown or blue [#permalink]

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23 Oct 2015, 00:25

Bunuel wrote:

AmoyV wrote:

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves? (1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1.

Merging topics.

Please refer to the discussion above.

If we do it by taking fractions, i.e. 3/7 X , 4/7 X , 2/3Y AND 1/3 Y, we do not get the same answer. Could you please advice?

Re: Each member of a pack of 55 wolves has either brown or blue [#permalink]

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23 Oct 2015, 00:34

Bunuel wrote:

shadabkhaniet wrote:

Not able to understand the line " If there are more than 3 blue-eyed wolves with white coats"

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves?

Look at the matrix below:

Attachment:

The attachment Wolves.png is no longer available

"There are more than 3 blue-eyed wolves with white coats" means that # of wolves which have blue eyes AND white coats is more than 3. The question asks whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

(1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. Not sufficient on its own. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1. Not sufficient on its own.

(1)+(2) When taken together we get the flowing matrix:

Attachment:

The attachment Wolves (1)+(2).png is no longer available

Notice that x and y must be integers (they represent some positive multiples for the ratios given in the statements).

So, we have that 3y+7x=55. After some trial and error we can find that this equation has only 3 positive integers solutions: y=2 and x=7 --> 3y+7x=6+49=55; y=9 and x=4 --> 3y+7x=27+28=55; y=16 and x=1 --> 3y+7x=48+7=55;

Now, the third solution (x=1) is not valid, since in this case # of wolves which have blue eyes AND white coats becomes 3x=3, so not more than 3 as given in the stem. As for the first two cases, in both of them 7x is more than 3y (49>6 and 28>27), so we can answer definite YES, to the question whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

Answer: C.

Hope it's clear.

with fractions i get E as the answer

Attachments

20151023013242.jpg [ 114.11 KiB | Viewed 1775 times ]

Not able to understand the line " If there are more than 3 blue-eyed wolves with white coats"

Each member of a pack of 55 wolves has either brown or blue eyes and either a white or a grey coat. If there are more than 3 blue-eyed wolves with white coats, are there more blue-eyed wolves than brown-eyed wolves?

Look at the matrix below:

"There are more than 3 blue-eyed wolves with white coats" means that # of wolves which have blue eyes AND white coats is more than 3. The question asks whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

(1) Among the blue-eyed wolves, the ratio of grey coats to white coats is 4 to 3. Not sufficient on its own. (2) Among the brown-eyed wolves, the ratio of white coats to grey coats is 2 to 1. Not sufficient on its own.

(1)+(2) When taken together we get the flowing matrix:

Notice that x and y must be integers (they represent some positive multiples for the ratios given in the statements).

So, we have that 3y+7x=55. After some trial and error we can find that this equation has only 3 positive integers solutions: y=2 and x=7 --> 3y+7x=6+49=55; y=9 and x=4 --> 3y+7x=27+28=55; y=16 and x=1 --> 3y+7x=48+7=55;

Now, the third solution (x=1) is not valid, since in this case # of wolves which have blue eyes AND white coats becomes 3x=3, so not more than 3 as given in the stem. As for the first two cases, in both of them 7x is more than 3y (49>6 and 28>27), so we can answer definite YES, to the question whether there are more blue-eyed wolves (blue box) than brown-eyed wolves (brown box).

Answer: C.

Hope it's clear.

with fractions i get E as the answer

Can you please give TWO examples which satisfy both statements and the stem?
_________________

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