DS Problems Need help!

Expert replies

kguo: Junior | Next Rank: 30 Posts; Posts: 18; Joined: Mon Aug 03, 2009 8:17 am

by kguo » Sun Oct 11, 2009 5:57 pm

1. Is the measure of one of the interior angles of quadrilateral ABCD equal to 60?

(1) Two of the interior angles of ABCD are right angles.

(2) The degree measure of angle ABC is twice the degree measure of angle BCD.

I don't get why the answer is what is is... isn't two right angles inside a quadrilateral automatically a rectangle??

E

2. If X and Y are points on the number line, what is the value of x+y?

(1) 6 is halfway between x and y.

(2) y = 2x

I'm probably just interpreting the question wrong why is why i don't understand the answer.

a

Like this post

Source: Beat The GMAT — Data Sufficiency | Sun Oct 11, 2009 5:57 pm

mehravikas: Legendary Member; Posts: 1161; Joined: Mon May 12, 2008 2:52 amFollowed by: 1 member; Location: Sydney; Thanked: 23 times

by mehravikas » Sun Oct 11, 2009 8:08 pm

Question 2 is correct. consider points on the number line.

6 is halfway between x and y. therefore values could be:
0 - 6 - 12
3 - 6 - 9
2 - 6 - 10
-6 - 6 - 18

Remember you are not asked about individual values, you need to calculate the sum, which is always 12.

Like this post

bullzeye: Newbie | Next Rank: 10 Posts; Posts: 5; Joined: Tue Oct 06, 2009 10:36 am

by bullzeye » Mon Oct 12, 2009 6:49 am

The answer to 1 is also correct.

To your question - no a 2 right angles are not sufficient for a quadrilateral to be a rectangle. You can draw pictures if you want. If you have 2 right angles, the only other think you can take out of this is that the sum of die other two angles is 360 - 2x180 = 180
statement 2 is misleading, esp. considering it in combination with statement 1.

So we have rectangle with 2x90 deg. angles and LABC=2LBCD. Since we have two options:
LABC=90 (stmn 1), or LABC not one of the right angles.
in the first case we get answer "NO" to the qustion -> The angles will be as follows: 90, 45, 135, 90
in the second case the answer is "YES" -> 90, 90, 120,60 will be the measures of the quadrilateral.

So we still don't know. Which leaves us with "E". Remember on the GMAT for something to be sufficient we need to have one and only one solution.

Last edited by bullzeye on Mon Oct 12, 2009 1:01 pm, edited 4 times in total.

Like this post

NikolayZ: Master | Next Rank: 500 Posts; Posts: 124; Joined: Thu Jun 18, 2009 5:33 am; Thanked: 35 times

by NikolayZ » Mon Oct 12, 2009 7:19 am

P#1.

Actually I think that the answer is C.

1) stmt says that two of angles are right. we have 2 possibilities for a polygon :
Rectangle in which two right angles are opposite, and a trapezoid, in which left ( or right) pair of angles are 90. Other angles will be 180=x+y. Insufficient.
2) We only know that ABC=2BCD. insufficient.

(1) + (2)
We exclude the rectangle possibility, whereas 90*2 does not equal to 90 =)
then we have the only option that two right angles form one side, hence other two angles' sum =180, x+2x=180, x=60. Sufficient.

Or maybe i misunderstand smth ?

Like this post

mehravikas: Legendary Member; Posts: 1161; Joined: Mon May 12, 2008 2:52 amFollowed by: 1 member; Location: Sydney; Thanked: 23 times

by mehravikas » Mon Oct 12, 2009 11:38 am

1st one would still be 'E'..it is a really tricky question.

consider - 90, 90, 45, 135

Satisfies statement 1 and 2.

NikolayZ wrote:P#1.

Actually I think that the answer is C.

1) stmt says that two of angles are right. we have 2 possibilities for a polygon :
Rectangle in which two right angles are opposite, and a trapezoid, in which left ( or right) pair of angles are 90. Other angles will be 180=x+y. Insufficient.
2) We only know that ABC=2BCD. insufficient.

(1) + (2)
We exclude the rectangle possibility, whereas 90*2 does not equal to 90 =)
then we have the only option that two right angles form one side, hence other two angles' sum =180, x+2x=180, x=60. Sufficient.

Or maybe i misunderstand smth ?

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

563 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (563 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review