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

Redeem

BC

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Data Sufficiency |
Legendary Member
Posts: 1161
Joined: Mon May 12, 2008 2:52 am
Location: Sydney
Thanked: 23 times
Followed by:1 members

by mehravikas » Sun Oct 11, 2009 8:19 pm
I am not able to understand why 'D' is the answer.

From statement 1 - Can we assume the sides to be in the ratio 1:sqrt(3):2 ?
Top
Master | Next Rank: 500 Posts
Posts: 189
Joined: Thu Apr 03, 2008 2:03 pm
Location: USA
Thanked: 21 times

by rohan_vus » Mon Oct 12, 2009 1:44 am
Yes stmnt (1) is also sufficient . consider dropping a perpendicular from B onto AD .. Take M a point on line AD and draw a simple vertical line to connect to B . thus now u have tow right anngle traingles ..One is BMC ( right angle at M ) and other is BMD ( again right angle at M) ..

Now u can derive easily CM = DM - CD .. ==> 3.. coz DM is given by 30-60-90 degree rule and you already know BD , so DM = 9

Similarly BM = 3*(sqrt of 3).. Consider triangle BMC now..( given BM and CM.. you know its 60degree at angle BCA ...So easy to BC then now.. BC = 6 = CD
Top
Legendary Member
Posts: 1161
Joined: Mon May 12, 2008 2:52 am
Location: Sydney
Thanked: 23 times
Followed by:1 members

by mehravikas » Mon Oct 12, 2009 11:40 am
Can you draw the figure and add it as an attachment please?
rohan_vus wrote:Yes stmnt (1) is also sufficient . consider dropping a perpendicular from B onto AD .. Take M a point on line AD and draw a simple vertical line to connect to B . thus now u have tow right anngle traingles ..One is BMC ( right angle at M ) and other is BMD ( again right angle at M) ..

Now u can derive easily CM = DM - CD .. ==> 3.. coz DM is given by 30-60-90 degree rule and you already know BD , so DM = 9

Similarly BM = 3*(sqrt of 3).. Consider triangle BMC now..( given BM and CM.. you know its 60degree at angle BCA ...So easy to BC then now.. BC = 6 = CD
Top
Master | Next Rank: 500 Posts
Posts: 371
Joined: Fri Mar 06, 2009 2:48 am
Thanked: 27 times
GMAT Score:740

by 2010gmat » Thu Nov 05, 2009 6:41 am
stmt 1 is suff...no need to draw the figure...simply drop a prependicular from B on AD...say it meets AD at E...

BE/ BD = Sin 30 --calclate BE

(dC+EC = DE) --> DE/BD = Cos 30 we know ec and bd calculate dc...

now in triangle BEC we know both BE and BC

BE/BC = Tanx -- x comes out as 60

x = exterior angle = sum of two int angles

=> <cbd = <cdb => CD = BC = 6

2 is simple...both angles equal hence sides equal

answer shud be D
Top
Post new topic Post Reply
• Page 1 of 1