If x is a positive integer...

This topic has expert replies
User avatar
Master | Next Rank: 500 Posts
Posts: 253
Joined: Fri Dec 26, 2008 8:39 pm
Thanked: 8 times
Followed by:1 members

If x is a positive integer...

by BlindVision » Fri Jun 19, 2009 10:20 am
If x is a positive integer, is x<16 ?

1) x is less than the average (arithmetic mean) of the first ten positive integers.

2) x is the square of an integer.


OA=A
Life is a Test

Senior | Next Rank: 100 Posts
Posts: 89
Joined: Sat May 30, 2009 2:49 am
Thanked: 9 times

by SanjeevK » Fri Jun 19, 2009 10:47 am
IMO A
A: average of first ten positive integers is 5.
1: If x < 5, it means x is definitely less than 16. Sufficient
2: x can be 16, 25, 36 etc. Not sufficient

Legendary Member
Posts: 940
Joined: Tue Aug 26, 2008 3:22 am
Thanked: 55 times
Followed by:1 members

by iamcste » Fri Jun 19, 2009 11:17 am
SanjeevK wrote:A: average of first ten positive integers is 5.
average of first ten positive integers is 5.5 :D

User avatar
Master | Next Rank: 500 Posts
Posts: 253
Joined: Fri Dec 26, 2008 8:39 pm
Thanked: 8 times
Followed by:1 members

by BlindVision » Fri Jun 19, 2009 11:29 am
Good catch. If a set of numbers are evenly spaced then the median=average.
Life is a Test

Senior | Next Rank: 100 Posts
Posts: 89
Joined: Sat May 30, 2009 2:49 am
Thanked: 9 times

by SanjeevK » Sat Jun 20, 2009 6:27 pm
iamcste wrote:
SanjeevK wrote:A: average of first ten positive integers is 5.
average of first ten positive integers is 5.5 :D
I am such a dumb. My Bad. Guess I have to be careful.

Legendary Member
Posts: 940
Joined: Tue Aug 26, 2008 3:22 am
Thanked: 55 times
Followed by:1 members

by iamcste » Sun Jun 21, 2009 8:16 am
SanjeevK wrote:
iamcste wrote:
SanjeevK wrote:A: average of first ten positive integers is 5.
average of first ten positive integers is 5.5 :D
I am such a dumb. My Bad. Guess I have to be careful.
it happens... :D

User avatar
Master | Next Rank: 500 Posts
Posts: 385
Joined: Sun May 24, 2009 3:55 pm
Thanked: 11 times
GMAT Score:740

by Domnu » Thu Jun 25, 2009 3:55 pm
A:

The average of the first 10 numbers is 5.5...

(1 + 10) + (2 + 9) + (3 + 8) + (4 + 7) + (5 + 6) = 11 + 11 + 11 + 11 + 11 = 55,

so 55/10 = 5.5. If x < 5.5, x < 16 for sure.

Just because x is a perfect square, we can't say that x < 16. So we are done.
Have you wondered how you could have found such a treasure? -T