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Re: Math Problem(+/-) [#permalink]
09 Nov 2010, 07:05

3

This post received KUDOS

Expert's post

Sarang wrote:

Question:- will this get completed in a time span of 2 mins?

It will.

+ x y z 4 1 -5 m e 7 n 10 f 2 -4 5

Take an aggressive approach. First find out what you want to know: m + n m = 4 + z and n = e + y so you need 4 + z + e + y

Now, y is simple. 4 + y = -5 so y = -9 e and z are trickier. Looking at the 2nd column, if I have x, I can find e. x is simple. 4 + x = 1 so x = -3 Now, e + x = 7 which means e -3 = 7 so e = 10 Only z remains. e + z = 10 so 10 + z = 10 giving me z = 0 I have all I needed. 4 + z + e + y = 4 + 0 + 10 -9 = 5
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the simplest way to do this is through a series of successive substitutions. whenever there's a () in the working below, it means i have substituted a value that i found in an earlier step.

How will I know that The sum of some value from the first row and and some value from the first column is given in the intersection box of these values. What is the mechanism?
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How will I know that The sum of some value from the first row and and some value from the first column is given in the intersection box of these values. What is the mechanism?

This is a 3 by 3 matrix.

If you to really see how this works, paste the table in an excel - some value is the value on the intersection of 1st row and 1st column /1st row and 2nd column/1st row and 3rd column/1st row and 4th column/2nd row and 2nd columns/... and so on: That will be the sum of the other two values

eg: 1st row and 2nd column : x,4 --> 1, so x+4=1 1st row and 3rd column : y,4 --> -5, so y+4=-5 ....so on

How will I know that The sum of some value from the first row and and some value from the first column is given in the intersection box of these values. What is the mechanism?

If you are not aware of the concept of 'addition table', the mechanism isn't intuitive. It might take some time to figure out. On the bright side, you now know the mechanism behind an addition table and if some other such concept does crop up in your actual GMAT, they will explain you how to arrive at the values. Very rarely will you see ambiguity in actual GMAT questions (If it does arise, they are quick to fix it.) So just know what this concept is and move on.
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Re: In the addition table shown above [#permalink]
12 Nov 2011, 11:56

So I took the GMAT prep today, for the first time, and despite scoring Q50, I was totally baffled by this question.

In hindsight, it is actually very simple, but it showed up as my second quant question. I have no clue what an addition table is and I just started at the damn matrix for a minute not even sure where to begin.

Almost derailed my test, but fortunately I pulled it together. But yea, if you have no idea what an addition table is, then this question is not intuitive.

After reading the first line explaining what is meant by an addition table, I quickly solved this in under 100 seconds. Damn!

This is called an addition table. An addition table is where numbers in the first row get added to numbers in the first column to give the results given in the grid e.g. 4 + X = 1, E + Y = N etc.

Re: In the addition table shown above, what is the value of m+n [#permalink]
26 Apr 2012, 18:24

Q # 2 on my GMAT Prep test # 1... spent 5 minutes trying to figure it out and still couldn't. Now I am worrying more than ever about such ridiculous questions....

Re: In the addition table shown above, what is the value of m+n [#permalink]
26 Apr 2012, 22:44

Expert's post

mk0991 wrote:

Q # 2 on my GMAT Prep test # 1... spent 5 minutes trying to figure it out and still couldn't. Now I am worrying more than ever about such ridiculous questions....

You don't have to worry. If this question was a part of GMAT at some time, it was a very very long time back. GMAT has been evolving and now if they use a term such as 'addition table', they are not going to assume that you know what it is. They will explain you what an addition table is i.e. they will tell you something like this" "An addition table is where numbers in the first row get added to numbers in the first column to give the results given in the grid e.g. 4 + X = 1, E + Y = N etc." The stats related to every question are monitored and if they see inconsistencies, they filter them out e.g. if they see people getting more than Q49 but sitting on this 500 - 600 level question for 5 mins, they will figure out why and take action. In GMAT, the intent of the question will be very clear. You will only have to worry about 'how to get the answer' not 'what do they want'.
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m = z + 4 and n = y + e so to find m+ n we need values of z,y,e x + 4 = 1 => x = -3 x + e= 7 => e = 7 - x = 10 z + e = 10 => z = 10 -e = 0 y + 4 = -5 => y = -9

So, m = z+ 4 = 0 + 4 =4 n = y + e = -9 + 10 = 1 so, m+n=5

Re: In the addition table shown above, what is the value of m+n [#permalink]
15 Jan 2013, 01:50

Attachment:

addition table.jpg [ 20.45 KiB | Viewed 2577 times ]

We do not have to calculate value of any variable here. The solution can be simplified as below: m=z+4 and n=y+e Hence m+n = z+4+y+e = (y+4) + (z+e) From yellow cell (y+4) = -5 From green cell (z+e) = 10