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# What is the probability of selecting a clean number from a

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Current Student
Joined: 29 Jan 2005
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What is the probability of selecting a clean number from a [#permalink]  26 Oct 2005, 06:52
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100% (01:26) correct 0% (00:00) wrong based on 2 sessions
What is the probability of selecting a clean number from a set of integers containing all multiples of 3 between 1 and 99, inclusive?

1. A clean number is an integer divisible by only 2 factors, one of which is greater than 2.
2. A clean number must be odd.
Manager
Joined: 01 Aug 2005
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A? Because statement one is pretty much telling us that the number is a prime. You dont need statement 2 because all primes are odd.
Manager
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Re: DS ProjectGMAT #99 [#permalink]  26 Oct 2005, 15:27
GMATT73 wrote:
What is the probability of selecting a clean number from a set of integers containing all multiples of 3 between 1 and 99, inclusive?

1. A clean number is an integer divisible by only 2 factors, one of which is greater than 2.
2. A clean number must be odd.

D.

Too simple to be true I know kaplan will have a catch for me.
Manager
Joined: 17 Sep 2005
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A for me!

set = {3,6,9,12,...96,99}

1) We know only prime #'s have just two factors - 1 and the number itself.
We also know from the set that 3 is the only prime in it and of course 3 is > 2

2) every other number in the set is odd.
NOT SUFF => A
Manager
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mbaqst wrote:
A for me!

set = {3,6,9,12,...96,99}

1) We know only prime #'s have just two factors - 1 and the number itself.
We also know from the set that 3 is the only prime in it and of course 3 is > 2

2) every other number in the set is odd.
NOT SUFF => A

In case wont be the probability of selecting a clean number be 1/2.
Senior Manager
Joined: 05 Oct 2005
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In case 2 u mean?

2. A clean number must be odd.

This says it will be odd, but in this case does not fully define a "clean number"

I guess the question is a little vague and confusing
VP
Joined: 06 Jun 2004
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Re: DS ProjectGMAT #99 [#permalink]  26 Oct 2005, 20:04
GMATT73 wrote:
What is the probability of selecting a clean number from a set of integers containing all multiples of 3 between 1 and 99, inclusive?

1. A clean number is an integer divisible by only 2 factors, one of which is greater than 2.
2. A clean number must be odd.

1. Clean number is defined as a prime number here. Sufficient.
2. Clean number is defined as an odd number here. Sufficient.
Senior Manager
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As far as I know, if the answer to a DS question is D, both 1) and 2) must yield the same value...

TeHCM, technically, you are right, but i doubt ETS would ever create such a question...
Do correct me if i'm wrong
Current Student
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OA is A. I am just tooo exhausted to type in the OE after a 14 hr workday. Will post it word-for-word ver batem after gaining some sanity over the weekend.
Manager
Joined: 01 Aug 2005
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Quote:
1. Clean number is defined as a prime number here. Sufficient.
2. Clean number is defined as an odd number here. Sufficient.

You are right about statement 1, it defines what a clean number is. Please look carefully at statement 2 though, it doesnt define a clean number as odd, it says a clean number must be odd. That =/= clean numbers are all odd numbers.

1. A clean number is an integer divisible by only 2 factors, one of which is greater than 2.
2. A clean number must be odd.

Think of it this way:
"A clean number is an integer divisible by 4"
"A clean number must be even"

^^
The latter doesnt mean that all even numbers are clean, and we already know that all of the numbers are even thanks to statement one.
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