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Is this something which is understood?

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by bfman » Mon Jul 20, 2009 12:04 pm
Referring to Page 237 Question 159 on Official Guide 12th Edition.

Is it true that when a question asks "How many prime numbers?" in a GMAT exam, it is understood that they are referring to only one instance of that prime number?

In this specific question, 5 occurs twice and hence I answered "E".

However, the correct answer according to these folks is "D" because they counted "5" only once.

Clarification is appreciated! Thank you.
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by xilef » Mon Jul 20, 2009 3:24 pm
It would usually say 'unique prime numbers' or 'different'
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by bfman » Mon Jul 20, 2009 4:28 pm
xilef wrote:It would usually say 'unique prime numbers' or 'different'
It doesn't :(
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Re: Is this something which is understood?

by tohellandback » Mon Jul 20, 2009 6:43 pm
bfman wrote:Referring to Page 237 Question 159 on Official Guide 12th Edition.

Is it true that when a question asks "How many prime numbers?" in a GMAT exam, it is understood that they are referring to only one instance of that prime number?

In this specific question, 5 occurs twice and hence I answered "E".

However, the correct answer according to these folks is "D" because they counted "5" only once.

Clarification is appreciated! Thank you.
IMO it depends upon the question
if a question asks " how many prime factors are there for 25". then you count only one 5.

if a question asks how prime numbers are there in the set {2,2,5}, answer should be three.

and of course if the question clearly mentions "distinct", you need to count the prime nos only once
The powers of two are bloody impolite!!
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by bfman » Tue Jul 21, 2009 11:07 am
But I have seen to be inconsistent in the Official Guide, in some places when they ask for prime factors they count all instances and in other instances they don't. And it does not say 'unique' or 'distinct' either. Simple "How many prime factors?"
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by Stuart@KaplanGMAT » Tue Jul 21, 2009 12:17 pm
It's the wording of the question that tells us we only count each number once:

"How many prime numbers between 1 and 100 are factors of 7150?"

The number 5 only appears once in the list of numbers from 1 to 100, so we only count it once when we answer the question.

If the question had been:

"7150 has how many prime factors?"

we would have counted each instance of 5 separately.
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by bfman » Tue Jul 21, 2009 2:25 pm
Thank you Stuart! I guess am not used to looking for so much detail :)
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