Lesson: Avoiding Common Mistakes - Part I

Comment on Avoiding Common Mistakes - Part I

Thank you. That was really helpful

Just to clarify, for don't overcalculate it says to not calculate the statement just determine if there is sufficient information to answer the question.

By that logic 4.25x-11.75=14.75 should be sufficient? If not, how do you evaluate sufficiency without calculating?
gmat-admin's picture

The target question asks "Does x = 6?"

IF we were to solve the equation, 4.25x - 11.75 = 14.75, we'd get ONE solution. At that point, we'd be able to definitively answer the target question.

Since we COULD answer the target question with certainty, that statement is sufficient.

All we need to know here is that the equation 4.25x - 11.75 = 14.75 will yield exactly one solution. Given this, we don't have to solve the equation for x.

Does that help?

Cheers,
Brent

Ohhhhhhhhh, I got it now. Basically we have sufficient information to answer yes/no to the target question with certainty, regardless of the outcome for x.
gmat-admin's picture

Exactly!

thanks

Hi Brent, just on overcalculating, what if the equation solving for x in the option doesn't equal 6? for example when we solve for x we get x= 3, so that is not sufficient right?
gmat-admin's picture

If the target question asks "Does x = 6?" and statement 1 says "x + 1 = 4", then statement 1 would still be sufficient, because we can still answer the target question with absolute certainty.

That is, I can provide an definitive answer to the target question: NO, x definitely does NOT equal 6.

You're not alone. Many students compare the answer to the target question with the answer to the sufficiency question. This is covered starting at 3:28 in the above video.

Cheers,
Brent

Great explanation, got that! so when the Q says "is x=6", it means can you answer if either x is or not equal to 6 with certainty. thanks!
gmat-admin's picture

Exactly!

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