D/S Number testing

[gmatwork]

In D/S questions that deal with Odds/Evens numbers and Prime numbers, should be we testing for only positive values and not consider negative values?

I have noticed that in some test questions, when the question stem says Odd/Even integers then the solution suggested testing both positive and negative values. I found this a lot in gmatclub quant tests.

[jnelson0612]

Yes, odds and evens can be positive or negative (and zero is even, so consider zero also), and thus it would make sense to consider testing both of those types of numbers.

On the other hand, if the numbers you can test with are restricted to ONLY prime numbers, then you don't have to worry about negatives. The smallest prime number is two and all primes are positive. Good question!

[gmatwork]

Thank you!

Another question regarding the type of numbers to be used for D/S question will depend on what that D/S question is dealing with -

a) for Odd/Even - Odd and Even
b) Inequality - Extreme values and boundary values (bounds of ineq)
c) Sign, absolutes (>0 <0) PNZ
d) powers, roots - proper fractions, integers, 0 and 1
e) addition/ subtraction - Both pos, neg with a difference in relative sizes

Also one of the MGMAT lab talks about FIZ (when do we need to use FIZ???

In above types we will use integer Vs number depending on the question. Please let me know if I missed out any major category of D/S questions. Coming up with the right set of value will save a lot of time on D/S.

[jnelson0612]

Thank you!

Another question regarding the type of numbers to be used for D/S question will depend on what that D/S question is dealing with -

a) for Odd/Even - Odd and Even
b) Inequality - Extreme values and boundary values (bounds of ineq)
c) Sign, absolutes (>0 <0) PNZ
d) powers, roots - proper fractions, integers, 0 and 1
e) addition/ subtraction - Both pos, neg with a difference in relative sizes

Also one of the MGMAT lab talks about FIZ (when do we need to use FIZ???

In above types we will use integer Vs number depending on the question. Please let me know if I missed out any major category of D/S questions. Coming up with the right set of value will save a lot of time on D/S.

This looks good to me! For D, don't forget that maybe you will use an actual square root, such as sqrt 2. There is a good example of this in OG12 #169.

FIZ can be relevant if you are trying to decide if a value is an integer, so you try fractions, integers, and zero.

[gmatwork]

Thank you!

[tim]

:)