Is this GRE question wrong??

[frankqfrank]

I believe the explanation shows that the 70 degree value is drawn in the wrong spot.

Picture of problem

This is from a Kaplan practice test CD

 

[compnovice]

you are right....

 

[frankqfrank]

it turns out that where they drew the 70 is also a 70 degree angle given the answer, but I don't think you could solve that only assuming the 70 degree value for the angle where the 70 is drawn

 

[compnovice]

Is this an actual GRE question or a practice test?

 

[dullard]

Is that an actual GRE question? Or is it a question from a GRE study manual?

 

[Syringer]

Yeah it should be to the right.

 

[frankqfrank]

a practice test from Kaplan on CD

 

[Tifababy]

I don't think you can solve it given the problem. I came up with a bunch of equations, but you need one more value before you can solve it.

 

[LegendKiller]

Originally posted by: frankqfrank
it turns out that where they drew the 70 is also a 70 degree angle given the answer, but I don't think you could solve that only assuming the 70 degree value for the angle where the 70 is drawn

Is there some type of rule to geometry that we are forgetting? If not, then there isn't any way that you could get 110 from the interior angle with where the 70 is currently placed.

 

[Syringer]

Originally posted by: frankqfrank
it turns out that where they drew the 70 is also a 70 degree angle given the answer, but I don't think you could solve that only assuming the 70 degree value for the angle where the 70 is drawn

No...if x = 40, then the adjacent angle to x is 50..assuming that's a right angle, so 50+70+70 = 190..so the one that is marked as 70 should be 60

Originally posted by: LegendKiller

Originally posted by: frankqfrank
it turns out that where they drew the 70 is also a 70 degree angle given the answer, but I don't think you could solve that only assuming the 70 degree value for the angle where the 70 is drawn

Is there some type of rule to geometry that we are forgetting? If not, then there isn't any way that you could get 110 from the interior angle with where the 70 is currently placed.

No.

 

[dullard]

Originally posted by: frankqfrank
a practice test from Kaplan on CD

Then don't worry about it. I didn't look closely, but I think you are correct. You need one more bit of information. Such as the fact that the side (mostly vertical) lines are parallel, one of the inner angles, or something else.

 

[dullard]

Originally posted by: Syringer
No...if x = 40, then the adjacent angle to x is 50..assuming that's a right angle, so 50+70+70 = 190..so the one that is marked as 70 should be 60

I don't think that is intended to be a right angle.

 

[Syringer]

Originally posted by: dullard

Originally posted by: Syringer
No...if x = 40, then the adjacent angle to x is 50..assuming that's a right angle, so 50+70+70 = 190..so the one that is marked as 70 should be 60

I don't think that is intended to be a right angle.

You mean the angle on the bottom left? It certainly is drawn to be a right angle..of course that usually doesn't mean anything.

 

[dullard]

Originally posted by: Syringer
You mean the angle on the bottom left? It certainly is drawn to be a right angle..of course that usually doesn't mean anything.

If we knew it was a right angle, then things would be a bit different. But as drawn it could be 89°, and you'd never be able to see it. In fact, it CANNOT be 90°, it must be 80°.

 

[LegendKiller]

The big rule with these tests is that you can never assume anything from the picture. When I took the gmat they loved to toss in stuff like this (albeit correctly labled angles) to throw you off.

Never assume an angle is any certain degree by just the picture.

 

[Vegitto]

What level is this? This is easy.

 

[Vegitto]

Originally posted by: LegendKiller
The big rule with these tests is that you can never assume anything from the picture. When I took the gmat they loved to toss in stuff like this (albeit correctly labled angles) to throw you off.

Never assume an angle is any certain degree by just the picture.

QFT! If it says x degrees, assume that, but if it looks like a right angle but doesn't carry the little thingie that tells you it is, don't assume it.

 

[Syringer]

Originally posted by: dullard

Originally posted by: Syringer
You mean the angle on the bottom left? It certainly is drawn to be a right angle..of course that usually doesn't mean anything.

If we knew it was a right angle, then things would be a bit different. But as drawn it could be 89°, and you'd never be able to see it.

Exactly..my basic point was that the angle labeled as 70 degrees is not 70 degrees even with strong assumptions..

 

[dullard]

Originally posted by: Syringer
Exactly..my basic point was that the angle labeled as 70 degrees is not 70 degrees even with strong assumptions..

I still don't get you. The left triangle is 70°, 70°, and 40°. The bottom triangle is 40°, 110°, and 30°. The right-hand triangle is 40°, 70°, and 70°. (Using all small triangles for clarity). Where is the problem.

Of course, we can't get to this answer from the data given. But since we know the answer, we can check that everything is possible if x=40°.

The bottom left corner is 40°+40°=80°. Don't assume it is 90°. In fact it CANNOT be 90°. It must be 80° using the biggest left-hand triangle.

 

[Ilmater]

Originally posted by: Syringer

Originally posted by: dullard

Originally posted by: Syringer
No...if x = 40, then the adjacent angle to x is 50..assuming that's a right angle, so 50+70+70 = 190..so the one that is marked as 70 should be 60

I don't think that is intended to be a right angle.

You mean the angle on the bottom left? It certainly is drawn to be a right angle..of course that usually doesn't mean anything.

Guys, how can you be missing this? The triangle that is made TELLS YOU that it's not a 90 degree angle. The other two angles making up that triangle are 70 and 30, meaning that angle is 80 degrees. So, those two lines aren't perpendicular.

I have no idea what the answer is. I don't honestly think you can answer it without at least one more data point somewhere.

Edit: I see that someone else has caught on to the fact that it's an 80 degree angle.

 

[Toastedlightly]

If the 70* was in the middle part, we could know what X is...

 

[DrPizza]

An easy way to look at it is that you could simply move the vertex (40 degrees) on the right triangle to the left, maintaining the 40 degree angle, but changing the value of x.

 

[Ilmater]

Originally posted by: Vegitto
QFT! If it says x degrees, assume that, but if it looks like a right angle but doesn't carry the little thingie that tells you it is, don't assume it.

Thanks for the news flash. I will stop assuming that test questions are lying to confuse me. That so explains my previous poor performance on tests.

Thank you, sir, for setting me straight.

 

[Otaking]

These diagrams for the GRE / GMAT are never drawn to scale, especially with GMAT's data sufficiency questions. A parallelogram that appears to be a square could really be a rectangle, so watch out.

Also, never assume that lines are parallel unless told so...

 

[Toastedlightly]

Originally posted by: Otaking
These diagrams for the GRE / GMAT are never drawn to scale, especially with GMAT's data sufficiency questions. A parallelogram that appears to be a square could really be a rectangle, so watch out.

Also, never assume that lines are parallel unless told so...

I think the issue is the misplaced 70*