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GMAT Tip of the Week: No Resolution!

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GMAT Tip of the Week: No Resolution! [#permalink]

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FROM Veritas Prep Blog: GMAT Tip of the Week: No Resolution!
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So you have a few more days to commit to your New Year’s Resolution, and if you’re like most people you have something like 35 days until you break it. Resolutions don’t often stick, but if your New Year’s Resolution is to apply to business school in 2014, and if as part of that resolution you’re planning to get a high GMAT score, you’re in luck:

Data Sufficiency problems don’t need resolutions.

Or perhaps better put, they’re problems that don’t always need to be resolved. As long as you know that you could finish the problem, you don’t need to finish it (kind of like once you’ve proven to yourself by January 16 that you *could* make it to the gym by 6am every day this year, you’ll decide that that’s enough and start sleeping in). That’s because Data Sufficiency questions are about whether you could get an answer, not about what the answer actually is. Consider this question:

What is the value of x?

(1) x^2 – 5x – 5 = 0

(2) x > 0

While you *could* do all the work to solve for x, you could also pretty lazily answer C without resolving the problem by factoring statement 1 and incorporating statement 2. How? Since the quadratic in statement 1 has a negative for the non-x term, then the parentheses when you factor it will look like:

(x + ___)(x – ____)

Meaning that there is one positive and one negative value of x. So there are two solutions – a positive and a negative – for statement 1, and clearly statement 2 is no good on its own. But taken together, you know that of the two solutions that statement 1 gives you, it has to be the positive solution based on the definition given in statement 2. So even if you didn’t resolve the quadratic in statement 1, you can get to the answer (C) quickly, saving valuable time and energy for later questions in the quant section – or for fun and relaxation after your study session since you did make that resolution to do 20 problems a day in 2014.

_____________________________________________________________

Now a caveat – use this advice carefully, because although you may not need to resolve some Data Sufficiency problems, hard problems will reward those who are resolute. Consider this problem, which should look similar:

What is the value of x?

(1) x^2 – 4x + 4 = 0

(2) x > 0

In statement 1, you can actually factor that into: (x – 2)(x – 2) = 0, which means that x MUST equal 2, making statement 1 sufficient alone (and the answer A). So don’t go crazy not doing any work. If you don’t know for certain that you can avoid the work, do the work. But as you practice with Data Sufficiency, resolve to avoid at least some resolution. Make 2014 the year of efficiency (then the year of admission-cy).

Happy New Year from the GMAT Tip of the Week team! We resolve to be back next week with even more useful GMAT strategies to help make your 2014 successful.

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Re: GMAT Tip of the Week: No Resolution! [#permalink]

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New post 21 Nov 2014, 10:00
I understand the point of the article, but what would be the solution for " x^2 – 5x – 5 = 0" where it will be positive and negative?
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Re: GMAT Tip of the Week: No Resolution! [#permalink]

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New post 24 Nov 2014, 11:55
Kris88 wrote:
I understand the point of the article, but what would be the solution for " x^2 – 5x – 5 = 0" where it will be positive and negative?


You would have to use the quadratic equation if you actually wanted to solve it.
Your two solutions of x would equal [(5+ √45) / 2] & [(5 - √45) / 2]

approx: (x - 5.854) (x + 0.854 )
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Re: GMAT Tip of the Week: No Resolution! [#permalink]

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New post 24 Nov 2014, 12:14
Kris88 wrote:
I understand the point of the article, but what would be the solution for " x^2 – 5x – 5 = 0" where it will be positive and negative?


tdotmba wrote:
Kris88 wrote:
I understand the point of the article, but what would be the solution for " x^2 – 5x – 5 = 0" where it will be positive and negative?


You would have to use the quadratic equation if you actually wanted to solve it.
Your two solutions of x would equal [(5+ √45) / 2] & [(5 - √45) / 2]

approx: (x - 5.854) (x + 0.854 )


You actually don't have to solve. Sum of roots = 5 and product is -ve. So definitely one of them is +ve and other one is -ve and +ve root is more than -ve root by 5.
And as quadratic equations are only defined for real numbers, we will be having only real number solution.
So statement 1 will not be sufficient.

So statement 2 will be required to solve the DS question. Answer will be C)
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GMAT Tip of the Week: No Resolution! [#permalink]

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New post 24 Nov 2014, 12:33
kinjiGC wrote:
Kris88 wrote:
I understand the point of the article, but what would be the solution for " x^2 – 5x – 5 = 0" where it will be positive and negative?


tdotmba wrote:
Kris88 wrote:
I understand the point of the article, but what would be the solution for " x^2 – 5x – 5 = 0" where it will be positive and negative?


You would have to use the quadratic equation if you actually wanted to solve it.
Your two solutions of x would equal [(5+ √45) / 2] & [(5 - √45) / 2]

approx: (x - 5.854) (x + 0.854 )


You actually don't have to solve. Sum of roots = 5 and product is -ve. So definitely one of them is +ve and other one is -ve and +ve root is more than -ve root by 5.
And as quadratic equations are only defined for real numbers, we will be having only real number solution.
So statement 1 will not be sufficient.

So statement 2 will be required to solve the DS question. Answer will be C)



Kris88 said he understood the article but just wanted to know what the two solutions would be anyways (I suppose in case a quadratic question appeared in PS to solve for actual value rather than DS) :)
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Re: GMAT Tip of the Week: No Resolution! [#permalink]

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New post 09 Jan 2018, 23:02
Re: GMAT Tip of the Week: No Resolution!   [#permalink] 09 Jan 2018, 23:02
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