|
Author |
Message |
|
TAGS:
|
|
|
Manager
Joined: 15 Aug 2006
Posts: 56
Followers: 1
Kudos [?]:
0
[0], given: 0
|
an integer > 1 that is not prime is called composite. If [#permalink]
 26 Nov 2006, 16:07
an integer > 1 that is not prime is called composite. If the 2 digit integer n is greater than 20, is n composite?
1. the ten digits of n is a factor of the units digit of n
2. the ten digit of n is 2.
|
|
|
|
|
|
|
Senior Manager
Joined: 20 Feb 2006
Posts: 376
Followers: 1
Kudos [?]:
0
[0], given: 0
|
From 1) There are no prime numbers between 20 and 100 where the tens digit is a factor of the units digit therefore n must be composite. SUFF
From 2) n could be 23 and therefore prime or 24 and therefore composite so INSUFF.
A for me
|
|
|
|
|
|
Manager
Joined: 24 Jun 2006
Posts: 63
Followers: 1
Kudos [?]:
1
[0], given: 0
|
I think Answer is C
For eg 13, The 10th place (1) is a factor of units place(3)
Statements 1 and 2 together give the answer
|
|
|
|
|
|
VP
Joined: 25 Jun 2006
Posts: 1185
Followers: 1
Kudos [?]:
16
[0], given: 0
|
A for me too.
imagine the number is xy.
x >= 2, y > 0.
if x is a prime, then y must also be the same prime. so 11 is a factor.
if x is not a prime, then x has a factor which is also a factor of y. and hence a factor of this number xy.
so xy must have another factor other than itself and 1. so xy is a composite.
2. is Insuff. take 23. 24.
|
|
|
|
|
|
Senior Manager
Joined: 08 Jun 2006
Posts: 347
Location: Washington DC
Followers: 1
Kudos [?]:
5
[0], given: 0
|
This is a good one..
A for me too
|
|
|
|
|
|
Manager
Joined: 03 Jul 2005
Posts: 199
Location: City
Followers: 1
Kudos [?]:
0
[0], given: 0
|
an integer > 1 that is not prime is called composite. If the 2 digit integer n is greater than 20, is n composite?
1. the ten digits of n is a factor of the units digit of n
2. the ten digit of n is 2.
A?
From 1. 99 / 99 / 33 / 22 /66 etc.... meets the rule, the tens digit 9 is a factor of the units digit 9? But we cannot consider 13, since the integer is greater than 20. SUFF
From 2. n could be 24 (composite) or 23 (prime) INSUFF
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
close
