m+n

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 345
Joined: Wed Mar 18, 2009 6:53 pm
Location: Sao Paulo-Brazil
Thanked: 12 times
GMAT Score:660

m+n

by shibal » Thu Jun 25, 2009 6:29 pm
What is m+n?

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


OA: 5
Source: — Problem Solving |

User avatar
Master | Next Rank: 500 Posts
Posts: 472
Joined: Sun Mar 29, 2009 6:54 pm
Thanked: 56 times

by ssmiles08 » Thu Jun 25, 2009 6:50 pm
You add each number of 1 row to its respective column.

x = -2
y = -9
z = 0

e = 10
f = 5

n is obtained by adding y to e which in this case is -9+10 = 1
m is obtained by adding z to 4 which in this case is 4

so m+n = 4+1 = 5.

Master | Next Rank: 500 Posts
Posts: 345
Joined: Wed Mar 18, 2009 6:53 pm
Location: Sao Paulo-Brazil
Thanked: 12 times
GMAT Score:660

by shibal » Thu Jun 25, 2009 6:55 pm
ssmiles08 wrote:You add each number of 1 row to its respective column.
could you kindly please show how to do that? by the answers u gave i can't really figure it out... sorry :oops:

User avatar
Master | Next Rank: 500 Posts
Posts: 472
Joined: Sun Mar 29, 2009 6:54 pm
Thanked: 56 times

by ssmiles08 » Thu Jun 25, 2009 7:07 pm
shibal wrote:
ssmiles08 wrote:You add each number of 1 row to its respective column.
could you kindly please show how to do that? by the answers u gave i can't really figure it out... sorry :oops:
sure.

I don't have my regular excel spreadsheet, so you might have to make yourself a chart on paper or something.

you have to add 4 to x to produce 1.

4 + x = 1; say in this case x = -3

now we know x. lets add x to e to produce 7
-3 + e = 7; e= 10

f+x = 2

f - 3 = 2; f = 5

now we know e, f, x.

4 + y = -5; y = -9

y + e = n; -9 + 10 = 1 (this is the value we need)

y + f = -4, since we already figured out y and f, this can stand as our verification to see that we calculated y and f correct. -9 + 5 = -4 (YES)

z = 0, b/c (z + f) = 5 since f = 5, z = 0. Similarly with z + e = 10. e is 10, z = 0.

from this we can conclude that 4 + 0 = 4(m)

so m = 4, n= 1. 4 + 1 = 5

note that we really didn't need to calculate all of the values in the chart, but it helps as a checking point during the exam.

-hope this helps.