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# M09 #23

Author Message
Current Student
Joined: 26 Jun 2006
Posts: 124
Schools: Ross Class of 2012
WE 1: Consumer Goods / IT
WE 2: Retail / Logistics
Followers: 1

Kudos [?]: 37 [1] , given: 8

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19 Nov 2008, 10:17
1
KUDOS
Quote:
The price of a mobile phone of model A increased by 15% from last year while the price of a mobile phone of model B decreased by 25% from last year. Is the current price of a mobile phone of model A bigger than that of a mobile phone of model B?

1. Last year the price of a mobile phone of model B was 10 percent bigger than that of a mobile phone of model A
2. Last year model A cost $10 more than model B (C) 2008 GMAT Club - m09#23 * Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient * Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient * BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient * EACH statement ALONE is sufficient * Statements (1) and (2) TOGETHER are NOT sufficient S1 allows to express current prices of both models in terms of one variable and compare them. For example, if $$A$$ is the last year's price of model A and $$B$$ is the last year's price of model B, then: $$\begin{eqnarray*} B_{current} &=& 0.75B = 1.1A*0.75\\ A_{current} &=& 1.15A\\ \end{eqnarray*}$$ Therefore, the current price of B is less than the current price of A. The question of course assumes that neither phone is given out for free. S2 is obviously sufficient. If model A was more expensive than model B and model A gained in price while model B depreciated, then model A is still more expensive than model B. Don't S1 and S2 run counter to each other?? How can the cost of A last year be$10 more than B (S2) but the price of model B last year be 10% more than A (S1)???
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Joined: 29 Aug 2007
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26 Nov 2008, 15:11
sharmar wrote:
Quote:
The price of a mobile phone of model A increased by 15% from last year while the price of a mobile phone of model B decreased by 25% from last year. Is the current price of a mobile phone of model A bigger than that of a mobile phone of model B?

1. Last year the price of a mobile phone of model B was 10 percent bigger than that of a mobile phone of model A
2. Last year model A cost $10 more than model B (C) 2008 GMAT Club - m09#23 * Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient * Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient * BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient * EACH statement ALONE is sufficient * Statements (1) and (2) TOGETHER are NOT sufficient S1 allows to express current prices of both models in terms of one variable and compare them. For example, if $$A$$ is the last year's price of model A and $$B$$ is the last year's price of model B, then: $$\begin{eqnarray*} B_{current} &=& 0.75B = 1.1A*0.75\\ A_{current} &=& 1.15A\\ \end{eqnarray*}$$ Therefore, the current price of B is less than the current price of A. The question of course assumes that neither phone is given out for free. S2 is obviously sufficient. If model A was more expensive than model B and model A gained in price while model B depreciated, then model A is still more expensive than model B. Don't S1 and S2 run counter to each other?? How can the cost of A last year be$10 more than B (S2) but the price of model B last year be 10% more than A (S1)???

Thats true. Statement 1 and 2 both cannot go togather.
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Joined: 04 Jan 2008
Posts: 914
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24 Apr 2009, 22:48
If the price of a mobile phone of model $$A$$ increased by 15% from last year and the price of a mobile phone of model $$B$$ decreased by 25% from last year, is the current price of a mobile phone of model $$A$$ greater than that of a mobile phone of model $$B$$ ?

1. Last year, the price of a mobile phone of model B was 10 percent greater than that of a mobile phone of model A
2. Last year, model A cost $10 more than model B is it A? OE never talks about condition no (2) and OA given is D _________________ http://gmatclub.com/forum/math-polygons-87336.html http://gmatclub.com/forum/competition-for-the-best-gmat-error-log-template-86232.html Director Joined: 01 Apr 2008 Posts: 897 Name: Ronak Amin Schools: IIM Lucknow (IPMX) - Class of 2014 Followers: 28 Kudos [?]: 600 [0], given: 18 Re: M09#23 [#permalink] ### Show Tags 25 Apr 2009, 00:56 should be D. 1) difference is in terms of percentage so whatever is the absolute figure the relation will be the same for price of A and B >> Suff 2) difference is in terms of absolute value. But the lesser absolute value(B) is decreasing and the higher absolute value(A) is increasing. So A will always be greater than B. ( Note, if A is less than B and if A is increasing and B is decreasing then this condition will be insufficient, I have explained it below ). Actual problem: eg. price of A is 11 => after 15% increase it is something greater than 11. price of B is 1 => after 25% decrease it is something less than 1. A > B eg. price of A is 110 => after 15% increase it is something greater than 110. price of B is 100 => after 25% decrease it is something less than 75. A > B. Sufficient. So, D. Lets see the corollary, that is if it is given that B is 10 more than A. eg. price of A is 1 => after 15% increase it is 1.15. price of B is 11 => after 25% decrease it is 8.25 A < B. eg. price of A is 100 => after 15% increase it is 115. price of B is 110 => after 25% decrease it is 82.5. A > B. So, in this case this condition will be insufficient. nitya34 wrote: If the price of a mobile phone of model $$A$$ increased by 15% from last year and the price of a mobile phone of model $$B$$ decreased by 25% from last year, is the current price of a mobile phone of model $$A$$ greater than that of a mobile phone of model $$B$$ ? 1. Last year, the price of a mobile phone of model B was 10 percent greater than that of a mobile phone of model A 2. Last year, model A cost$10 more than model B

is it A?

OE never talks about condition no (2)

and OA given is D
Manager
Joined: 10 Apr 2008
Posts: 53
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10 Jun 2009, 01:11
But you're picking a case that works.

What if A = 1
and B = 11

Then new A = 1.15
new B = 8.25

The OA is wrong.

Economist wrote:
should be D.
1) difference is in terms of percentage so whatever is the absolute figure the relation will be the same for price of A and B >> Suff

2) difference is in terms of absolute value. But the lesser absolute value(B) is decreasing and the higher absolute value(A) is increasing. So A will always be greater than B. ( Note, if A is less than B and if A is increasing and B is decreasing then this condition will be insufficient, I have explained it below ).

Actual problem:

eg. price of A is 11 => after 15% increase it is something greater than 11.
price of B is 1 => after 25% decrease it is something less than 1.
A > B

eg. price of A is 110 => after 15% increase it is something greater than 110.
price of B is 100 => after 25% decrease it is something less than 75.
A > B.

Sufficient.
So, D.

Lets see the corollary, that is if it is given that B is 10 more than A.
eg. price of A is 1 => after 15% increase it is 1.15.
price of B is 11 => after 25% decrease it is 8.25
A < B.

eg. price of A is 100 => after 15% increase it is 115.
price of B is 110 => after 25% decrease it is 82.5.
A > B.
So, in this case this condition will be insufficient.

nitya34 wrote:
If the price of a mobile phone of model $$A$$ increased by 15% from last year and the price of a mobile phone of model $$B$$ decreased by 25% from last year, is the current price of a mobile phone of model $$A$$ greater than that of a mobile phone of model $$B$$ ?

1. Last year, the price of a mobile phone of model B was 10 percent greater than that of a mobile phone of model A
2. Last year, model A cost $10 more than model B is it A? OE never talks about condition no (2) and OA given is D Manager Joined: 14 Dec 2009 Posts: 79 Followers: 1 Kudos [?]: 37 [0], given: 20 Re: M09 #23 [#permalink] ### Show Tags 10 Feb 2010, 00:49 The statements must be changed! They are confusing and take precious time during the test! They cannot contradict each other! Manager Joined: 17 Jan 2010 Posts: 59 Concentration: Entrepreneurship, Strategy GMAT 1: 730 Q49 V41 WE: Consulting (Consulting) Followers: 2 Kudos [?]: 43 [0], given: 6 Re: M09 #23 [#permalink] ### Show Tags 10 Feb 2010, 01:15 The price of a mobile phone of model A increased by 15% from last year while the price of a mobile phone of model B decreased by 25% from last year. Is the current price of a mobile phone of model A bigger than that of a mobile phone of model B? 1. Last year the price of a mobile phone of model B was 10 percent bigger than that of a mobile phone of model A 2. Last year model A cost$10 more than model B

(C) 2008 GMAT Club - m09#23

* Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
* Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
* BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
* EACH statement ALONE is sufficient
* Statements (1) and (2) TOGETHER are NOT sufficient

Here's an explanation,

Let Price Cell Phone A last year be X , and that of Model B be Y
According to Information given in the question

Model A's current price = X + 15/100X , Model B's current price = Y - 25/100Y

Now lets work with the statements given.

1) Last year the price of a mobile phone of model B was 10 percent bigger than that of a mobile phone of model A

Y = 10/100X , so we have a relationship between Y and X , Substitute this value of Y in Model B's current price

Model B's current price = 10/100X - (25/100*10/100)X, which is clearly lesser than Model A's current price X + 15/100X - hence sufficient.

2)Last year model A cost \$10 more than model B

X = Y + 10 or Y = X - 10 , again substitute this value in Model B's current Price and we can compare the two to tell if X's current price is greater or less than B's current price.

No point getting bogged down in calculations.

Hence answer - D, each statement alone is sufficient.
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Re: M09 #23   [#permalink] 10 Feb 2010, 01:15
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# M09 #23

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