when do you try non-integer values?

Question

For example: 
What is the value of y?
(1) x^2 - y^2 = 5
(2) x and y are positive integers

answer is C.

But, if (2) was reworded to "x and y are positive numbers", than wouldn't the answer be E? Since there is an infinitely of numbers you can square that are 5 units apart.

Not sure if there is an easy answer to this, but if you are plugging in number (especially DS problems) when should you try non-integers?

Bunuel · Answer

Yes, if we were not told that x and y are positive integers, the answer would be E. The answer would be E even if we were told that x and y are integers (omitting the word "positive"). In this case y could be +/-2.

As for your other question, if you are not told that variables are integers, then you should certainly consider non-integer values too.

ccooley · Answer

The quick, somewhat flippant answer is 'you should try non-integers whenever the problem doesn't tell you not to.' But that's not an easy thing to notice! The human brain isn't very good at noticing what  isn't  there. You'll probably notice if the problem tells you that the numbers  are  integers. But it's harder to notice when the problem  doesn't  say that.

One mnemonic that may help you remember is "FROZEN": Fractions, Roots, One, Zero, Extremes, Negatives. Those are the most common weird cases that you may need to test while solving a Data Sufficiency problem. You won't need to test all of them on every problem (and you wouldn't have time to, anyways!) but quickly thinking through the mnemonic before you submit your answer can help you think of cases you may have missed.

when do you try non-integer values?

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