Data sufficiency help

[snehavenkat]

gmat official guide 13th edition
56th problem.
What is the Value of z in the triangle above?
1. x+y=139 ---> Sufficient x+y+z= 180 substitute x+y
2. y+z=108 ---> x+y+z=180 substitute y+z and u get the value of x then u can rewrite as z=108-y n again substitute it and can get the value of z.
According to the guide the correct answer is A.
please explain why not D..

[theCodeToGMAT]

To find: "z"

x + y + z = 180*

Statement 1:
x + y = 139
Z = 180 - 139 = 41
SUFFICIENT

Statement 2:
y+z = 108
x = 180-108 = 72
You cannot comment on value of "z"
INSUFFICIENT


Answer [spoiler]{A}[/spoiler]

[theCodeToGMAT]

2. y+z=108 ---> x+y+z=180 substitute y+z and u get the value of x then u can rewrite as z=108-y n again substitute it and can get the value of z.

we found out value for "x" & not "y" .. so we cannot do anything by z=108-y

[[email protected]]

Hi snehavenkat,

In DS questions, when you're asked to find the "value" of something, the question is "really" asking if the value is consistent or inconsistent.

In this DS question, Fact 1 tells you x + y = 139, so if you "plug" that into x + y + z = 180, then you CAN figure out z (it equals 41) and that's the only possible answer. Thus, Fact 1 is SUFFICIENT.

In Fact 2, we're told that y + z = 108
So....there are possibilities....
y = 54, z = 54
y = 53, z = 55
etc.

Thus, z can be different values and there's no way to sure which one it actually is. Thus, Fact 2 is INSUFFICIENT.

GMAT assassins aren't born, they're made,
Rich

[sanju09]

gmat official guide 13th edition
56th problem.
What is the Value of z in the triangle above?
1. x+y=139 ---> Sufficient x+y+z= 180 substitute x+y
2. y+z=108 ---> x+y+z=180 substitute y+z and u get the value of x then u can rewrite as z=108-y n again substitute it and can get the value of z.
According to the guide the correct answer is A.
please explain why not D..

We cannot find z from y + z = 108, hence (2) is not sufficient.

[Newaz111]

Hi snehavenkat,

In DS questions, when you're asked to find the "value" of something, the question is "really" asking if the value is consistent or inconsistent.

In this DS question, Fact 1 tells you x + y = 139, so if you "plug" that into x + y + z = 180, then you CAN figure out z (it equals 41) and that's the only possible answer. Thus, Fact 1 is SUFFICIENT.

In Fact 2, we're told that y + z = 108
So....there are possibilities....
y = 54, z = 54
y = 53, z = 55
etc.

Thus, z can be different values and there's no way to sure which one it actually is. Thus, Fact 2 is INSUFFICIENT.

GMAT assassins aren't born, they're made,
Rich

Thank you so much Rich. Now I found the logic.