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:

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C

Information from table:
d+z=m (1)
e+y=n (2)

need to find "m+n"

A: d+y=-3, INSUFF - no information about n
B: e+z=12, INSUFF - no information about m

Adding 1 and 2 (under information)

(d+y)+(e+z)=m+n=12-3=9 (use both A and B)

There must be something I'm completely unaware of because how does box DY and box EZ relate to the box values the question asks for?

It's an an addition table. For example, e + y = n and d + z = m.

Hope it's clear.
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Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.


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

When you modify the original condition and the question, n+m=(e+y)+(d+z)=(e+z)+(y+d)=?. Then you need all 1) & 2) and therefore the answer is C.


 Once we modify the original condition and the question according to the variable approach method 1, we can solve approximately 30% of DS questions.
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Hi Bunuel: Can you please post similar problems on addition tables

Check other Addition/Subtraction/Multiplication Tables problems from our Special Questions Directory
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Hello. Why do we need both statements? Doesn't statement 2 suffice? Since we need to find n+m we can just find e+z which is given in statement 2. Am I missing something here? The addition/multiplication works only with the variables in the first row/column? Thanks.

Hi geo1230

e+z will give you entry for row below m or column beside n. These are entries against different additions and does not simply signify the value of row or column.

so to get the value of n you need e+y and for m you need d+z

To be honest I still don't get it. If e+y gives me n and d+z gives me m, then, likewise e+z should give the value of the cell that is below m and right next to n, which is the same as saying n+m.

Hi

The highlighted part above is correct, but part after that is not correct. How is that cell equal to sum of n+m?

Hello. I thought it worked like a coordinate system. For example, the value of the sum e+y is located in the cell where n is located which is the intersection of row e and column y. So the value of n+m is the cell where they intersect, so it can be found from the row e and column z, as in e+z. In the picture I am trying to show what I mean. With red is the logic of the sums, with yellow the target cells where the value of the sum is located and with blue is the reason I believe that statement 2 alone is sufficient. Hope it clarifies the line of thinking.

Hi Geo

Thanks for clarifying where you were coming from. But this table is NOT to be interpreted like this. Rather it is to be interpreted in the way I have depicted in the attached pic.

So, as you can see, 'n' is e+y and 'm' is d+z. But that third cell is just 'e+z', its NOT 'n+m'.

amanvermagmat Thank you for taking the time to clarify this. Now it's quite logical why my line of thinking is wrong. It's just that we don't have multiplication/addition tables in my country, so I bumped into these now with the GMAT. Thanks again and take a kudos as a thank you from me.

But doesn't d+y added with 1 gives m? And e+z subtracted from 1 n?

Bunuel, this one as well appear in Official Mock. Please tag this under GMAT Prep

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Added the tag. Thank you!
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