BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Gmatprep3 Problem

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Master | Next Rank: 500 Posts
Posts: 358
Joined: Thu Apr 18, 2013 9:46 am
Location: Jeddah, Saudi Arabia
Thanked: 42 times
Followed by:7 members
GMAT Score:730

Gmatprep3 Problem

by faraz_jeddah » Sun Sep 22, 2013 12:48 am
No Idea how to solve this.

Image
A good question also deserves a Thanks.

Messenger Boy: The Thesselonian you're fighting... he's the biggest man i've ever seen. I wouldn't want to fight him.
Achilles: That's why no-one will remember your name.
Top
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 1556
Joined: Tue Aug 14, 2012 11:18 pm
Thanked: 448 times
Followed by:34 members
GMAT Score:650

by theCodeToGMAT » Sun Sep 22, 2013 5:25 am
Edited:
Area of the BCE = √2/4

Answer [spoiler][/spoiler]

Sorry, earlier I made a wrong diagram which resulted in answer 1/2
Attachments
area.jpg
Last edited by theCodeToGMAT on Sun Sep 22, 2013 7:24 am, edited 1 time in total.
R A H U L
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 358
Joined: Thu Apr 18, 2013 9:46 am
Location: Jeddah, Saudi Arabia
Thanked: 42 times
Followed by:7 members
GMAT Score:730

by faraz_jeddah » Sun Sep 22, 2013 5:33 am
I am not sure what the logic you have used but the answer is incorrect.

OA is B
A good question also deserves a Thanks.

Messenger Boy: The Thesselonian you're fighting... he's the biggest man i've ever seen. I wouldn't want to fight him.
Achilles: That's why no-one will remember your name.
Top
User avatar
Legendary Member
Posts: 1556
Joined: Tue Aug 14, 2012 11:18 pm
Thanked: 448 times
Followed by:34 members
GMAT Score:650

by theCodeToGMAT » Sun Sep 22, 2013 5:53 am
faraz_jeddah wrote:I am not sure what the logic you have used but the answer is incorrect.

OA is B
Really??????? Can you please share the explanation.. I was very convinced that I was correct :|
R A H U L
Top
User avatar
Legendary Member
Posts: 1556
Joined: Tue Aug 14, 2012 11:18 pm
Thanked: 448 times
Followed by:34 members
GMAT Score:650

by theCodeToGMAT » Sun Sep 22, 2013 7:03 am
faraz_jeddah wrote:I am not sure what the logic you have used but the answer is incorrect.

OA is B
yes, correct.. the answer is indeed .. small mistake :)

I have edited my post which is just below the question.
R A H U L
Top
Junior | Next Rank: 30 Posts
Posts: 17
Joined: Mon Jul 22, 2013 4:40 pm
Thanked: 1 times

by runningguy » Sun Sep 22, 2013 7:25 am
I'm confused as to why the answer is not 1/2 (A=1/2(b)(h)).

b=1
h=1

A=1/2(1)(1)=1/2
Top
User avatar
Legendary Member
Posts: 1556
Joined: Tue Aug 14, 2012 11:18 pm
Thanked: 448 times
Followed by:34 members
GMAT Score:650

by theCodeToGMAT » Sun Sep 22, 2013 7:32 am
runningguy wrote:I'm confused as to why the answer is not 1/2 (A=1/2(b)(h)).

b=1
h=1

A=1/2(1)(1)=1/2
How did you find that base and height are 1?? that's not possible

if you say that you drew a perpendicular on BE from C and that weighted 1.. then the triangle is not possible as BC & CE are 1.. so perpendicular to BE from C must be less than 1.

if you say that you extended the C and dropped a perpendicular from E on the extended C line.. then also similar rule applies..

Refer my solution just below the question..
R A H U L
Top

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: Sun Jun 23, 2013 6:38 pm
Location: Palo Alto, CA
Thanked: 2867 times
Followed by:511 members
GMAT Score:800

by [email protected] » Sun Sep 22, 2013 12:33 pm
Hi All,

You might find this approach to be a bit easier; it's based on spotting a "hidden" 45/45/90 triangle...


Image


GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Top
Junior | Next Rank: 30 Posts
Posts: 17
Joined: Mon Jul 22, 2013 4:40 pm
Thanked: 1 times

by runningguy » Sun Sep 22, 2013 3:27 pm
theCodeToGMAT wrote:
runningguy wrote:I'm confused as to why the answer is not 1/2 (A=1/2(b)(h)).

b=1
h=1

A=1/2(1)(1)=1/2
How did you find that base and height are 1?? that's not possible

if you say that you drew a perpendicular on BE from C and that weighted 1.. then the triangle is not possible as BC & CE are 1.. so perpendicular to BE from C must be less than 1.

if you say that you extended the C and dropped a perpendicular from E on the extended C line.. then also similar rule applies..

Refer my solution just below the question..
I had incorrectly assumed that one of the legs that was equal to 1 was the height. After looking at my flash cards, I see that for an isosceles triangle, you can divide the hypotenuse by sqrt2 to find the length. This was a very tricky question for me.
Top
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Mon Sep 23, 2013 2:41 am
Image

In square ABCD, since s=1, BD = √2 and CF = √2/2.
It is given that CE=1.
Thus, EF = √2/2 + 1.

∆BED = (1/2)(BD)(EF) = (1/2)(√2)(√2/2 + 1) = (1/2)(1 + √2) = 1/2 + √2/2.

∆BCD = (1/2)(square ABCD) = 1/2.

Quadrilateral BEDC = ∆BED - ∆BCD = (1/2 + √2/2) - 1/2 = √2/2.

∆BCE = (1/2)(quadrilateral BEDC) = (1/2)(√2/2) = √2/4.

The correct answer is B.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 358
Joined: Thu Apr 18, 2013 9:46 am
Location: Jeddah, Saudi Arabia
Thanked: 42 times
Followed by:7 members
GMAT Score:730

by faraz_jeddah » Mon Sep 23, 2013 2:51 am
GMATGuruNY wrote:Image

In square ABCD, since s=1, BD = √2 and CF = √2/2.
It is given that CE=1.
Thus, EF = √2/2 + 1.

∆BED = (1/2)(BD)(EF) = (1/2)(√2)(√2/2 + 1) = (1/2)(1 + √2) = 1/2 + √2/2.

∆BCD = (1/2)(square ABCD) = 1/2.

Quadrilateral BEDC = ∆BED - ∆BCD = (1/2 + √2/2) - 1/2 = √2/2.

∆BCE = (1/2)(quadrilateral BEDC) = (1/2)(√2/2) = √2/4.

The correct answer is B.
Thanks Mitch! I must say it would be hard to figure this question out in less than 3 minutes.
A good question also deserves a Thanks.

Messenger Boy: The Thesselonian you're fighting... he's the biggest man i've ever seen. I wouldn't want to fight him.
Achilles: That's why no-one will remember your name.
Top
User avatar
Newbie | Next Rank: 10 Posts
Posts: 9
Joined: Mon Jul 06, 2009 2:08 am

by shinys » Tue Sep 24, 2013 6:19 pm
Rich,
Can you please help me understand how you figured out that 135 deg angle?
Top

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: Sun Jun 23, 2013 6:38 pm
Location: Palo Alto, CA
Thanked: 2867 times
Followed by:511 members
GMAT Score:800

by [email protected] » Tue Sep 24, 2013 6:36 pm
Hi shinys,

We're told that the sides BC=CD=CE=1 and we're told that BE=DE. This info tells us that the 2 triangles are IDENTICAL.

Since they're identical, their two "big angles" + the corner of the square = 360 degrees

2(Big angle) + 90 = 360
2(Big angle) = 270
Big angle = 135

Be on the lookout for the "special" right triangles in GMAT Quant questions; sometimes they're obvious, sometimes they're hidden.

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Top
User avatar
Senior | Next Rank: 100 Posts
Posts: 35
Joined: Sat Aug 31, 2013 1:29 pm
Thanked: 2 times
Followed by:1 members
GMAT Score:680

by Resp007 » Thu Sep 26, 2013 4:38 am
HI Rich,
I used GMATGuruNY approach and solved it correctly but as pointed its bit time consuming,
So looked into yours and couldn't understand how you found H.
How you were able to conclude its a 45-45-90 triangle please?

[email protected] wrote:Hi All,

You might find this approach to be a bit easier; it's based on spotting a "hidden" 45/45/90 triangle...


Image


GMAT assassins aren't born, they're made,
Rich
Top
User avatar
Senior | Next Rank: 100 Posts
Posts: 35
Joined: Sat Aug 31, 2013 1:29 pm
Thanked: 2 times
Followed by:1 members
GMAT Score:680

by Resp007 » Thu Sep 26, 2013 4:39 am
repeat post...
Last edited by Resp007 on Thu Sep 26, 2013 4:42 am, edited 1 time in total.
Top
Post new topic Post Reply