DS on equations

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r_walid
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Topic: DS on equations

Thu Nov 05, 2009 10:56 am

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Data sufficiency question on the following:
what is the value of n?

1) n(n+2) = 15
2) (n+2)^2=125

please explain your process.

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Bryant@VeritasPrep
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Thu Nov 05, 2009 12:26 pm

I would say that either equation alone is sufficient, since you have one unknown. _________________ Bryant Michaels MBA Admissions Consultant Veritas Prep

Abdulla
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Sat Nov 14, 2009 12:09 am

r_walid wrote: Data sufficiency question on the following: what is the value of n? 1) n(n+2) = 15 2) (n+2)^2=125 please explain your process. first stmt. we have quadratic equation, so almost always we will have two solutions. lets check. n^2+2n=15 n^2+2n-15=0 (n+5)(n-3)=0 n= -5, 3 Insufficient Second stmt. again .. let's check.. (n+2)(n+2)=125 n^2+4n+4=125 n^2+4n-121=0 we can see that n has two values too, so insufficient Combined, if we subtract stmt 1 from 2 we will get a linear equation with one variable, so we can solve it. IMO the answer is C _________________ Abdulla

enniguy
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Tue Nov 17, 2009 5:33 pm

r_walid wrote: Data sufficiency question on the following: what is the value of n? 1) n(n+2) = 15 2) (n+2)^2=125 please explain your process. I strongly think that you have mistyped statement 2. I might be wrong too . Statement 2 should have been: 2) (n+2)^2=25 In which case, answer is C because, 1) n could be 3 or -5. 2) n could be 3 or -7. Together, n=3.

Jarron11
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Wed Nov 18, 2009 1:34 pm

Agree with enniguy

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grockit_jake
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Thu Nov 19, 2009 5:46 pm

Right you need both to solve. Instead of solving for the 2 possible values of n for each and then comparing, you can solve both equations in terms of n^2, set equal and solve for n that way. _________________ Jake Becker Academic Director Grockit Test Prep http://www.grockit.com