9 factor of 2x :: Manhattan GMAT Forums

Posted: Sun May 11, 2008 5:21 pm

Hi,

If 9 is a factor of 2x, can I assume that x will have at least two 3's ?. Is it a valid assumption ?

Posted: Wed May 14, 2008 1:56 pm

Yes u can assume that,Its a valid assumption

Posted: Thu May 15, 2008 6:51 pm

Absolutely. Some part of the expression 2x must contain those two 3s, and it's clearly not 2. So it must be x.

Rey

Posted: Tue May 20, 2008 11:49 am

Provided it is specified that x is an integer.

Posted: Thu May 29, 2008 12:05 am

Cutlass makes a good point. If 9 is a factor of 2x, that means that when you divide 2x by 9, you get an integer (no remainder) as a result. Therefore, 2x must be an integer (an integer times an integer is an integer). But x itself may not be!

For example, if x is 4.5, then 2x is 9. 9 is a factor of 9. But x does not "contain" two 3s - it's not even an integer. :)