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Re: Number Property DS [#permalink]
27 Oct 2008, 02:28

Is it D?

stmt1: Excluding N^2, it has 4 factors. Two of these will be 1 and N. Two other factors are possible only when N is the square of a prime number. Suppose, N = p^2, then two other factors of N^2 will be p and N*p. Hence, sufficient.

stmt2: Excluding 2N, N has 3 factors. These will be 1, 2, N. That means, N itself is a prime number. Hence, sufficient.

Re: DS - number theory [#permalink]
03 Nov 2008, 01:41

B.

From stmt1: N^2 has 1, N and two more factors (excluding N^2). Both these factors could also be of N or, only one of them is of N. Hence, insufficient.

From stmt2: 2N has 1, 2 and N as factors (excluding 2N). Hence, N must be a prime number. Hence, sufficient.

Re: DS - number theory [#permalink]
03 Nov 2008, 02:53

scthakur wrote:

B.

From stmt1: N^2 has 1, N and two more factors (excluding N^2). Both these factors could also be of N or, only one of them is of N. Hence, insufficient.

From stmt2: 2N has 1, 2 and N as factors (excluding 2N). Hence, N must be a prime number. Hence, sufficient.

My friend in my opinion stmnt 1 is SUFF.....and 2 is also SUFF...so i picked D but OA is A

Re: DS - number theory [#permalink]
03 Nov 2008, 09:55

GODSPEED wrote:

scthakur wrote:

B.

From stmt1: N^2 has 1, N and two more factors (excluding N^2). Both these factors could also be of N or, only one of them is of N. Hence, insufficient.

From stmt2: 2N has 1, 2 and N as factors (excluding 2N). Hence, N must be a prime number. Hence, sufficient.

My friend in my opinion stmnt 1 is SUFF.....and 2 is also SUFF...so i picked D but OA is A

I need a break making too many silly mistakes today.

Yes, OA should be A.

In stmt2: if N = 4, 2N =8 and it has 1, 2, 4 as factors (excluding 8). But, N has 1,2,4 as factors. However, if N = 3, 2N = 6 and it has 1, 2,3 as factors (excluding 6). However, N has only 1 and 3 as factors. Hence, insufficient.

Re: DS - number theory [#permalink]
03 Nov 2008, 10:05

stmnt 2..if 2N=6 then say N=3, factors of 6 are 1, 2, 3 6<--not included , N=3 factors are 1 and 3..

if 2N=8 then factors are 1,2,4 8<--not included N=2 factors are 1 and 2

all stmnt 2 is say N is a prime number

I think D.

scthakur wrote:

GODSPEED wrote:

scthakur wrote:

B.

From stmt1: N^2 has 1, N and two more factors (excluding N^2). Both these factors could also be of N or, only one of them is of N. Hence, insufficient.

From stmt2: 2N has 1, 2 and N as factors (excluding 2N). Hence, N must be a prime number. Hence, sufficient.

My friend in my opinion stmnt 1 is SUFF.....and 2 is also SUFF...so i picked D but OA is A

I need a break making too many silly mistakes today.

Yes, OA should be A.

In stmt2: if N = 4, 2N =8 and it has 1, 2, 4 as factors (excluding 8). But, N has 1,2,4 as factors. However, if N = 3, 2N = 6 and it has 1, 2,3 as factors (excluding 6). However, N has only 1 and 3 as factors. Hence, insufficient.

Re: If N is a positive integer, not including N, how many [#permalink]
07 Feb 2014, 17:17

1

This post was BOOKMARKED

If N is a positive integer, not including N, how many factors does N have? (1) Not including N^2, N^2 has 4 factors -> N^2 (a perfect square) has a total of 5 factors => N has 3 factors in total (N is a perfect square of prime number). example: N = 4; N^2 = 16 (5 factors); N has 2 factors excluding N. example: N = 9; N^2 = 81 (5 factors); N has 2 factors excluding N. (2) Not including 2N, 2N has 3 factors -> 2N has a total of 4 factors For 2N to have a total of 4 factors, N can be 2^2 or (any other prime)^1 example: N = 4; 2N = 8 (4 factors);N has 2 factors excluding N. example: N = 3; 2N = 6 (4 factors); N has 1 factor excluding N. NOT SUFFICIENT. A.

gmatclubot

Re: If N is a positive integer, not including N, how many
[#permalink]
07 Feb 2014, 17:17

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