GMAT Data Sufficiency Walkthrough 📊

What I like about data sufficiency is that it encourages you to be thorough, exhaustive in your analysis.

Let me explain.

They're asking us, here is Y greater than one.

Now remember, for you to be able to answer this question as anything other than E or not sufficient in any way, I need to be able to answer this question conclusively.

So either always yes or always no.

If a million times yes and one time no, then A not sufficient.

Right?

I cannot answer the question, so I need to be exhaustive and thorough.

Now, these statements are truth.

When I consider these, statements either alone or in combination, will I be able to answer that question conclusively?

This is what I'm trying to find.

Now let me look at statement number one again.

It's evidence that is 100% true.

They're telling me that the absolute value of X minus 3 is less than Y minus root 2.

And I'll think, wow, that's a lot of algebra, or I have to try some numbers.

However, you may remember that absolute value of anything is non negative.

So I know for a fact, therefore, that the absolute value of x minus 3 is most definitely at least zero.

It cannot be negative.

So this is greater than or equal to zero.

So worst case scenario, it's zero.

And now they're telling me that Y minus root 2 is greater than this.

And therefore I know that y minus root 2 has to be greater than 0.

Okay?

Y minus root 2 is greater than the absolute value of something, and that absolute value is at least zero.

Therefore, this is at least zero.

And now if I rearrange this, I get that Y is greater than the root of 2.

I know that the root of 2 is approximately 1.4, and therefore y is definitely greater than 1.

Conclusively answered statement number one is sufficient.

Now, when I read this, on its own, X is greater than zero, less than three.

Well, how does X relate to Y?

I'm not provided with information until I reach statement number one, which is already sufficient on its own.

So alone statement number two is not sufficient, the correct answer is a.