DS2

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DS2

by kamalakarthi » Fri Oct 17, 2014 12:29 pm
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by Brent@GMATPrepNow » Fri Oct 17, 2014 1:04 pm
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The figure above shows two entries, indicated by m and n, in an addition table. What is the value of n + m?

(1) d + y = -3
(2) e + z = 12
Target question: What is the value of n + m?
Notice that the table tells us that m = d + z and that n = e + y
So, m + n = (d + z) + (e + y)
So we can REPHRASE the target question...
REPHRASED target question: What is the value of d + z + e + y?

Statement 1: d + y = -3
This information provides only half of the information we need.
We still need the values of z and e in order to find the sum of d + z + e + y
Since we cannot answer the REPHRASED target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: e + z = 12
This information provides only half of the information we need.
We still need the values of d and y in order to find the sum of d + z + e + y
Since we cannot answer the REPHRASED target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 1 tells us that d + y = -3
Statement 2 tells us that e + z = 12
So, d + z + e + y = (d + y) + (e + z) = (-3) + (12) = 9
Since we can answer the REPHRASED target question with certainty, the combined statements are SUFFICIENT

Answer = C

Cheers,
Brent
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by kamalakarthi » Fri Oct 17, 2014 6:34 pm
Brent, Thanks for the clear explanation!!!

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by j_shreyans » Sat Oct 18, 2014 4:27 am
Notice that the table tells us that m = d + z and that n = e + y
Hi Brent ,

Thanks for the explanation , but one thing that i need to know is how do we come to know m= d + z and n= e + y.

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by Brent@GMATPrepNow » Sat Oct 18, 2014 7:49 am
j_shreyans wrote:
Notice that the table tells us that m = d + z and that n = e + y
Hi Brent ,

Thanks for the explanation , but one thing that i need to know is how do we come to know m= d + z and n= e + y.
The question assumes that we know how an addition table works. Here's a self-explanatory diagram:

Image

Cheers,
Brent
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