341) Find area of triangle

Expert replies

ern5231: Master | Next Rank: 500 Posts; Posts: 226; Joined: Sun Aug 09, 2009 4:34 am

by ern5231 » Tue May 18, 2010 5:45 am

A rectangle ABCD has vertex E(of a triangle) on side AD. The other vertices of triangle, G and F, lie on the edge BC. The area of the rectangle is 24.What is the area of triangle GEF.
1) DC = 4, 2) GF = 1/3BC

Like this post

Source: Beat The GMAT — Data Sufficiency | Tue May 18, 2010 5:45 am

asamaverick: Master | Next Rank: 500 Posts; Posts: 106; Joined: Mon Sep 28, 2009 9:29 amFollowed by: 2 members; Location: Boston, MA; Thanked: 26 times; GMAT Score:700

by asamaverick » Tue May 18, 2010 7:12 am

[/img]

Given Area = 24.

1) DC = 4.
Since Area = 24, this only tells us that AD = BC = 6.
Not enough to know the area of triangle.
2) GF = 1/3 BC
Not knowing the actual length of at least one side we cannot calculate area of triangle.

Combining both gives. DC = 4. Hence BC = 6. Which gives GF = 2. This is enough to calculate the area of triangle.
Hence answer is C.

Like this post

raviki8208: Newbie | Next Rank: 10 Posts; Posts: 9; Joined: Mon May 10, 2010 1:23 am

by raviki8208 » Tue May 18, 2010 8:08 am

ern5231 wrote:A rectangle ABCD has vertex E(of a triangle) on side AD. The other vertices of triangle, G and F, lie on the edge BC. The area of the rectangle is 24.What is the area of triangle GEF.
1) DC = 4, 2) GF = 1/3BC

using 1 alone,
Area(GEF) = 1/2 * GF * DC. GF is unknown so unsufficient
using 2 alone
Given GF = 1/3 * BC

Area(GEF) / Area(XYGF) = ((1/2) * GF * DC) / (GF * DC) = 1/2
Area(XYGF) / Area(ABCD) = GF * DC / BC * DC = GF / BC= 1/3
Area(GEF)/Area(ABCD) = 1/6.. sufficient so Answer is B
what is OA?

Like this post

asamaverick: Master | Next Rank: 500 Posts; Posts: 106; Joined: Mon Sep 28, 2009 9:29 amFollowed by: 2 members; Location: Boston, MA; Thanked: 26 times; GMAT Score:700

by asamaverick » Tue May 18, 2010 9:11 am

raviki8208 wrote:
ern5231 wrote:A rectangle ABCD has vertex E(of a triangle) on side AD. The other vertices of triangle, G and F, lie on the edge BC. The area of the rectangle is 24.What is the area of triangle GEF.
1) DC = 4, 2) GF = 1/3BC

using 1 alone,
Area(GEF) = 1/2 * GF * DC. GF is unknown so unsufficient
using 2 alone
Given GF = 1/3 * BC

Area(GEF) / Area(XYGF) = ((1/2) * GF * DC) / (GF * DC) = 1/2
Area(XYGF) / Area(ABCD) = GF * DC / BC * DC = GF / BC= 1/3
Area(GEF)/Area(ABCD) = 1/6.. sufficient so Answer is B
what is OA?

You are right...it has to be B. I missed that part, drawing the rectangle XYGF makes it so much more clear.
Thanks.

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 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