OG- DS #128

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klamation: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Mon Jul 21, 2008 12:03 pm; GMAT Score:710

OG- DS #128

by klamation » Sat Aug 02, 2008 11:23 am

If x is an integer, is x|x| < 2x?

1) x < 0
2) x = -10

OA is D

Can someone explain why statement 1 is sufficient please?

If x = -1, then x|x| = -1 and 2x = -2, so the answer is NO
But, if x = -3, then x|x| = -9 and 2x = -6, so the answer is YES

Therefore, this statement should be NOT SUFFICIENT. What am I missing?

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Source: Beat The GMAT — Data Sufficiency | Sat Aug 02, 2008 11:23 am

rey.fernandez: GMAT Instructor; Posts: 83; Joined: Sun Mar 02, 2008 9:05 pm; Thanked: 21 times; Followed by:2 members

by rey.fernandez » Sun Aug 03, 2008 1:29 am

In my edition, the question stem reads:

If x is an integer, is x|x| < 2^x?

Check your text again...

With this question, (1) is sufficient because the left side of the inequality is negative while the right side is positive.

Rey Fernandez
Instructor
Manhattan GMAT

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klamation: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Mon Jul 21, 2008 12:03 pm; GMAT Score:710

by klamation » Sun Aug 03, 2008 6:49 am

Thanks, my book definitely has 2x instead of 2^x so mine must be a typo.

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eccentric: Senior | Next Rank: 100 Posts; Posts: 88; Joined: Tue Jul 15, 2008 1:43 am; Thanked: 3 times; Followed by:1 members; GMAT Score:590

by eccentric » Sun Aug 03, 2008 10:56 am

With the version of question given ....
1 is insufficient to answer the problem as
x< 0 means x can take following values -1, -2 ,-3,-4 etc
with -1 lhs > rhs
-2 lhs = rhs
-3 lhs < rhs
hence there is no unique solution set for this...
option reduced to BCE
with
2. x =-10 is sufficeint enough to conclude hence B must be answer
???? i m correct on this.....