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M01 #20 - Contradiction between between the two statement?

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Senior Manager
Joined: 20 Mar 2008
Posts: 452

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20 Aug 2009, 20:37
If Jim saved a total of $90 in 3 weeks, how much did he save in week 2? 1. Jim's average savings for the first 2 weeks were$20
2. Jim's first week's savings were half of his savings in week 2 and a third of his savings in week 3

* 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

OA is given as B. However, I think it St. 2 contradicts the information given in St.1.

The explanation given is:

Quote:
Suppose $$S_1$$ , $$S_2$$ , and $$S_3$$ are the amounts Jim saved for the first, second, and third week, respectively.

Statement (1) by itself is not sufficient. $$S_1+S_2=\40$$ . Although $$S_3$$ can be calculated, the value of $$S_2$$ cannot be calculated. Consider $$S_1=\20$$ and $$S_2=\20$$ or $$S_1=\5$$ and $$S_2=\35$$ .

Statement (2) by itself is sufficient. From Statement (2): $$S_2 =2 * S_1$$ and $$S_3 = 3 * S_1$$
$$S_1 + 2 * S_1 + 3 * S_1 = \90$$
$$6 * S_1 = \90$$
$$S_1 = \15$$

Solving for $$S_2$$ gives a value of $$S_2 = 2 * S_1 = 2 * 15 =\30$$ .

The problem is with St.2, $$S_1 + S_2 = 15 + 30 = 45$$. This is not 40, as per St. 1
Manager
Joined: 30 May 2009
Posts: 216

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20 Aug 2009, 20:49
Agreed. The answer is clearly B.

Stmt 1 and Stmt 2 contradict each other. This, I remember reading somewhere, will never happen on real GMAT exam.
Current Student
Joined: 18 Jun 2009
Posts: 356
Location: San Francisco

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21 Aug 2009, 14:14
are we sure ?

from what I heard is that only when the answer is D the two statements should result in the same answer.

Senior Manager
Joined: 20 Mar 2008
Posts: 452

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22 Aug 2009, 13:26
gmanjesh wrote:
are we sure ?

from what I heard is that only when the answer is D the two statements should result in the same answer.

No, that's wrong info. Neither of the two statements can contradict each other, irrelevant of what the answer is.

The idea is that the two statements are giving you some additional information, to figure out if the problem is solvable or not. They cannot, must not, add any more ambiguity to the problem.
Manager
Joined: 10 Sep 2009
Posts: 112

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20 Oct 2009, 02:58
That's a really interesting thing to notice.

I have been preparing the gmat for 2 months and I was never noticed such a thing... I guess I just missed the information.

Thank you very much for this tip
CIO
Joined: 02 Oct 2007
Posts: 1218

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20 Oct 2009, 05:06
Sorry, I somehow missed this one. What if we change S1 to "Jim's average savings for the first 2 weeks were \$22.5"? We won't have a contradiction then. Will it work?
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Re: M01 #20 - Contradiction between between the two statement?   [#permalink] 20 Oct 2009, 05:06
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M01 #20 - Contradiction between between the two statement?

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