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Help on a Data Sufficiency Problem

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wlvoh Newbie | Next Rank: 10 Posts Default Avatar
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Help on a Data Sufficiency Problem

Post Wed Feb 07, 2007 6:37 pm
I got the following question on a practice test, and cannot figure it out. The correct answer, according to PR, is A. I thought initially it was D. If someone can explain to me the rationale, most importantly why B is not sufficient, I would greatly appreciate it.

" A bowl is filled with consecutively numbered tiles from 1 to x. Joe pulls out a tile
and uses it to contruct sequence Q, which consists of 10 consecutive integers starting
with the number drawn. If Joe then selects one number from Sequence Q, what is the
probability that the selected number is a multiple of 3?

1.) The last number in sequence Q is a prime number that is less than 20.

2.) x (is less than or equal to) 10

"

Thanks.

wlvoh

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Post Thu Feb 08, 2007 10:54 am
Yeah - I assumed that too as I first read it, but then I realized that didn't make sense when I looked at the statements, so I read it again to figure out what was really going on. As Mark said, the language isn't "clean" enough to be an official question - they do try to trap you on the test, but not through deliberately convoluted language.

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Post Wed Mar 28, 2007 5:53 am
It's A...Very much in the way explained...If the sequence starts with multiples of 3 then it will have 4 elements which are divisible by 3. Then the probabiltiy becomes 4/10

If the sequence starts with any other number (numbers which are not multiples of 3) then the probability becomes 3/10

Hence B is insufficient alone

A is sufficient

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Post Thu Feb 08, 2007 10:54 am
Yeah - I assumed that too as I first read it, but then I realized that didn't make sense when I looked at the statements, so I read it again to figure out what was really going on. As Mark said, the language isn't "clean" enough to be an official question - they do try to trap you on the test, but not through deliberately convoluted language.

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Cybermusings Legendary Member Default Avatar
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Post Wed Mar 28, 2007 5:53 am
It's A...Very much in the way explained...If the sequence starts with multiples of 3 then it will have 4 elements which are divisible by 3. Then the probabiltiy becomes 4/10

If the sequence starts with any other number (numbers which are not multiples of 3) then the probability becomes 3/10

Hence B is insufficient alone

A is sufficient

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wlvoh Newbie | Next Rank: 10 Posts Default Avatar
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Post Thu Feb 08, 2007 5:06 am
The question as I typed it was verbatim from the practice test. A huge thanks to Stacey on the explanation. I took the wording to mean he actually drew 10 tiles for his sequence, thus he would have had 1 through 10. The source of this is a practice test from Princeton Review.

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Post Thu Feb 08, 2007 12:43 am
What is the source on this one?

Totally agree that this one is more convoluted than is typical on the real thing. We (ManhattanGMAT) have a special set of questions we call Challenge Questions - half of them are harder than anything you'd actually see on the test. (And we say they're really just for "fun" or challenging yourself, but they're not part of the main curriculum.) Maybe other companies also have something like this and this question came from that?

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