Is H a prime number

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neilcao: Junior | Next Rank: 30 Posts; Posts: 24; Joined: Mon Nov 29, 2010 3:46 pm

by neilcao » Mon Feb 21, 2011 7:47 am

Is H a prime number?

1. any factor of H is > H ^1/2
2. any factor of H is > H/2

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Source: Beat The GMAT — Data Sufficiency | Mon Feb 21, 2011 7:47 am

mk101: Senior | Next Rank: 100 Posts; Posts: 58; Joined: Fri Oct 22, 2010 1:05 am; Location: Bhopal; Thanked: 1 times; GMAT Score:710

by mk101 » Mon Feb 21, 2011 7:53 am

IMO D. Basically, what we need to know here is that for any prime number there is no factor less than sqrt of that number. SO from statement A we get that the number is prime and even from the statement B we get that the number is prime.

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Night reader: Legendary Member; Posts: 1337; Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members; Thanked: 127 times

by Night reader » Mon Feb 21, 2011 8:00 am

for me D too

st(1) factors of primes are the primes and 1; H-prime, 1 OR H>sqrt(H) answer No as the lowest is 2 and 1<sqrt(2) although 2>sqrt(2) Sufficient
st(2) the same explanation as in st(1) H>H/2, No as the lowest is 2 and 2>2/2 BUT 1=2/2 Sufficient

neilcao wrote:Is H a prime number?

1. any factor of H is > H ^1/2
2. any factor of H is > H/2

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findmimi: Junior | Next Rank: 30 Posts; Posts: 19; Joined: Mon Jul 26, 2010 10:52 pm

by findmimi » Mon Feb 21, 2011 8:45 am

I am confused.
As 1 is a factor of any integer, I cannot think of any number that would qualify 1)
For the same reason, the only positive integer that qualifies 2) is 1 - which would be sufficient to answer the question stem as 1 is not a prime.

Please can anyone help?

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ankur.agrawal: Master | Next Rank: 500 Posts; Posts: 261; Joined: Wed Mar 31, 2010 8:37 pmFollowed by: 3 members; Location: Varanasi; Thanked: 11 times

by ankur.agrawal » Mon Feb 21, 2011 9:28 am

1) Since u cant think of any number that would qualify. So obviously not prime. Sufficient. Actually since 2 is the first prime & that is also >1 . So u know none of the primes will work with (1). So H cannot be prime.

2) 1 is not prime . So again H is not prime.Sufficient.

findmimi wrote:I am confused.
As 1 is a factor of any integer, I cannot think of any number that would qualify 1)
For the same reason, the only positive integer that qualifies 2) is 1 - which would be sufficient to answer the question stem as 1 is not a prime.

Please can anyone help?

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