GMAT Math

Hi all,

Quick question -

Prime numbers - are negative numbers considered Prime (-2, -3, etc.)? Does that make any sense?

Also, I'm in the thick of my identifying weaknesses and practicing those weaknesses part of my prep. Two areas I continue to find difficulty in:
1. Word Problems which involve assigning variables - i stumble over those questions when I see them even though I completely understand how to arrive at an answer. These are questions I believe I should be answering correctly. Any suggestions on how to strengthen this area? I've reviewed the GMAT Prep Now modules over again and did all the GMAT Quant 2nd Edition questions on Word Problems thus far.

2. Data Sufficiency, especially involving arithmetic questions. I find that I either make careless mistakes (i.e. not take in all the rules / limits from question stem (x is positive, x is integer etc.) or I find it difficult to definitely conclude that an equation or question arrives at just one answer. Any suggestions for strengthening DS?

Thanks everyone!

NEGATIVE NUMBERS ARE NOT PRIME NUMBERS.

First prime number is 2.

I think you're asking why negative numbers are not prime...? At the most unsatisfying and superficial level, the answer lies in the definition: it's a prime number if it's an integer, and if it has exactly two factors. So following the definition, -2 is not prime because it has four factors.

From an historical point of view, I can't tell you why people began to look at breaking up numbers into their factors, but, once they did, it added no new info to consider the negative numbers. If you succeeded in finding the factors of 30, then you knew at once the factors of -30. So essentially nothing was lost by ignoring negatives.

Today factoring techniques are used in cryptography. Think about that next time you test for divisibility by 7.

misterholmes

Yes, negatives are not primes.

As for the other stuff... it sounds like practice is your answer. If you understand the stuff but are not performing well, you need to dive deep into the problems you are getting wrong and see what types of mistakes you are making. Are there patterns?