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Math Question

by Codebreaker2k » Mon Feb 18, 2013 12:53 pm
What is the value of k - m ?

1. (k-m)^3=8
2. (k-m)^5=32


Now, the official answer to this question is D (each statement is true by itself). My initial thought was two equations and two variables means substitution, C. Experts can you please advise....
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by Brent@GMATPrepNow » Mon Feb 18, 2013 1:03 pm
Codebreaker2k wrote:What is the value of k - m ?

1. (k-m)^3=8
2. (k-m)^5=32


Now, the official answer to this question is D (each statement is true by itself). My initial thought was two equations and two variables means substitution, C. Experts can you please advise....
The big difference here is that we aren't asked to find the individual values of k and m. We're asked to find the difference k-m.

If we let k-m = "thing," we can rephrase the entire question to read:

What is the value of thing?

1. (thing)^3=8
Thing must equal 2, so statement 1 is sufficient.

2. (thing)^5=32
Thing must equal 2, so statement 2 is sufficient.

Answer: D

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Brent
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by Brent@GMATPrepNow » Mon Feb 18, 2013 1:08 pm
The notion that two equations are required whenever we have two variables in a Data Sufficiency question is a myth (and a common trap on the GMAT).
This (and other myths) is covered in these two free videos:

Data Sufficiency Myths - part I: https://www.gmatprepnow.com/module/gmat- ... cy?id=1106
Data Sufficiency Myths - part II: https://www.gmatprepnow.com/module/gmat- ... cy?id=1107

Cheers,
Brent
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