Lesson: Choosing a Statement

Comment on Choosing a Statement

Hey Brent!
Thank you for the awesome job at clear and simplified explanations. Based on this video, As soon as we looked at statement 2, I figured x=3. Following the no contradiction rule, I plugged in 3 for the x in statement 1 and the equation zeroed out. Will that be a sufficient reason to determine insufficiency for statement 1 since x can be any value when the equation zeroes out.
gmat-admin's picture

Hi abrahamic,

That strategy can get you in trouble.
Once you determine (from statement 2) that x = 3, then the sufficiency of statement 1 depends on whether it allows for more than one x-value.

Your question: "Will that be a sufficient reason to determine insufficiency for statement 1, since x can be any value when the equation zeroes out."

My answer: But, how many x-values will satisfy the equation?

If statement 1 were x - 3 = 0, then plugging in x = 3 (from statement 2) would find that this x-value satisfies the equation. Does this mean that statement 1 is not sufficient? No, statement 1 would definitely be sufficient.

Likewise, if statement 1 were x² - 6x + 9 = 0, then this statement would also be sufficient, since there's only one x-value (x = 3) that satisfies the equation.

This stuffs can be slippery. I am currently on 500, I need a minimum of 600 but I would like to aim for somewhere above 650. I plan to use only GMATPrepNow and the Official Guide. I want to prepare steadily until sometimes in early October to take the exam. Do you give a nod to this plan?
gmat-admin's picture

That seems like a reasonable plan.

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