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## is X odd if X^3 is odd??

This topic has 7 member replies
zealzoom Junior | Next Rank: 30 Posts
Joined
28 Jul 2006
Posted:
19 messages

#### is X odd if X^3 is odd??

Fri Nov 10, 2006 10:29 am
Hi ,

Do let me know if this is sufficient to answer the question,,,

Is X odd ??

X^3 is Odd,,,,

Cheers
zeal

kulksnikhil Senior | Next Rank: 100 Posts
Joined
23 May 2006
Posted:
58 messages
2
Sat Nov 11, 2006 2:37 am
zealzoom wrote:
that was the problem

is X odd

a) 2x-1 is odd

b) X^3 is odd ..

My answer was B and i was pretty sure about that, but correct answer was E and reason I have already given.

DS,, its real tough to get into it ,,,

Any help??

Zeal
Even I feel B is right answer... for a product to be even, atleast one of the integers must be even. So if both integers are odd then the product remains odd. For x^3 to be odd, all 3 should be odd... so x has to be odd.

zealzoom Junior | Next Rank: 30 Posts
Joined
28 Jul 2006
Posted:
19 messages
Sat Nov 11, 2006 8:09 am
800guy wrote:
where did this question come from?
this was question in Kaplan GMAT test ....

zipper123 Newbie | Next Rank: 10 Posts
Joined
10 Oct 2006
Posted:
8 messages
Fri Nov 10, 2006 12:24 pm
zealzoom wrote:
Hi ,

Do let me know if this is sufficient to answer the question,,,

Is X odd ??

X^3 is Odd,,,,

Cheers
zeal
Yes it is sufficient.

Assuming X is an integer (positive or negative)

X^3 can only be odd if X itself is odd

because Odd times Odd is Odd

Even times Anything is Even.

_________________
==Still Working==

zealzoom Junior | Next Rank: 30 Posts
Joined
28 Jul 2006
Posted:
19 messages
Fri Nov 10, 2006 12:38 pm
naah thats the catch here!!!

I also think in the same way and this question seems very easy to me..

Here is the situation..

What if X = cube root 7 or cube root 3 ?? then X^3 will be odd but X itself is not an integer rather, it is an irrational number so no chance we cam certainly say that X is ODD,,,

Oh boy !! this line of reasoning really freaked me out.. let me know how do you feel ??

aim-wsc Legendary Member
Joined
20 Apr 2006
Posted:
2470 messages
Followed by:
14 members
85
Target GMAT Score:
801-
Fri Nov 10, 2006 2:28 pm
theses nothing wrong in zipper s reply.

he's right. because he assumed that X is an integer.
so technically given condition is not sufficient. we need to know whether X is am integer or not.

pls present the full problem.

_________________
Getting started @BTG?

Please do not PM me, (not active anymore) contact Eric.

zealzoom Junior | Next Rank: 30 Posts
Joined
28 Jul 2006
Posted:
19 messages
Fri Nov 10, 2006 9:33 pm
that was the problem

is X odd

a) 2x-1 is odd

b) X^3 is odd ..

My answer was B and i was pretty sure about that, but correct answer was E and reason I have already given.

DS,, its real tough to get into it ,,,

Any help??

Zeal

800guy Master | Next Rank: 500 Posts
Joined
27 Jun 2006
Posted:
354 messages
Followed by:
5 members
11
Fri Nov 10, 2006 9:38 pm
where did this question come from?

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