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

Redeem

OG2018 PS In the figure shown

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Senior | Next Rank: 100 Posts
Posts: 62
Joined: Wed Aug 09, 2017 3:54 pm

OG2018 PS In the figure shown

by lionsshare » Mon Aug 28, 2017 12:30 pm

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

Image


In the figure shown, AC = 2 and BD = DC = 1. What is the measure of angle ABD?

A. 15°
B. 20°
C. 30°
D. 40°
E. 45°

OA: C

Please share your solution for this problem.
Top
Source: — Problem Solving |
User avatar
Newbie | Next Rank: 10 Posts
Posts: 3
Joined: Tue Aug 10, 2010 8:03 am

by fmillar » Tue Aug 29, 2017 12:21 am
Hi there, here comes my first reply ! (let me know if I need to post answers differently)

1) Angle BDC = 60 as it is the complement of ADB (120+60=180)
2) BDC=60 then DBC + DCB = 120, but as BD=DC then DBC=DCB=60 (so an equilateral triangle)
3) Now check that AC =2 but DC=1 therefore AD=1 (AC-DC=2-1)
4) AD =1 but also BD =1 then triangle ADB is isosceles
5) If ADB =120 then DAB+ABD=60 (isosceles), as consequence DAB =30 and ABD=30
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3008
Joined: Mon Aug 22, 2016 6:19 am
Location: Grand Central / New York
Thanked: 470 times
Followed by:34 members

by Jay@ManhattanReview » Tue Aug 29, 2017 8:41 pm
lionsshare wrote:Image


In the figure shown, AC = 2 and BD = DC = 1. What is the measure of angle ABD?

A. 15°
B. 20°
C. 30°
D. 40°
E. 45°

OA: C

Please share your solution for this problem.
We have to find out the value /_ABD.

We know that AC = 2 and DC = 1, thus AD = AC - DC = 2 - 1 = 1

Thus, in ∆ABD, AD = BD = 1. Thus, it's an isosceles triangle.

/_ABD + /_BDA + /_DAB = 180

2*/_ABD + /_BDA = 180

/_ABD = (180 - 120)/2 = 30

The correct answer: C

Hope this helps!

Download free ebook: Manhattan Review GMAT Quantitative Question Bank Guide

-Jay
_________________
Manhattan Review GMAT Prep

Locations: New York | Barcelona | Manila | Melbourne | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8084
Joined: Sat Apr 25, 2015 10:56 am
Location: Los Angeles, CA
Thanked: 43 times
Followed by:29 members

by Scott@TargetTestPrep » Wed Nov 15, 2017 3:49 pm
lionsshare wrote:Image


In the figure shown, AC = 2 and BD = DC = 1. What is the measure of angle ABD?

A. 15°
B. 20°
C. 30°
D. 40°
E. 45°
Since AC = 2 and DC = 1, AD must be 1. Since BD = 1, this makes triangle ABD an isosceles triangle with angle D as the vertex angle and angles A and ABD as the base angles. We know that angles A and ABD are equal because the sides opposite them are equal. If we let each of the base angles = x, we can create the following equation:

x + x + 120 = 180

2x = 60

x = 30

Answer: C

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
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 Jun 12, 2018 4:12 pm
Hi All,

We're told that in the figure shown, AC = 2 and BD = DC = 1. We're asked for the measure of angle ABD.

To start, we know that the drawing is not to scale, so we cannot use the shapes in the picture to estimate an answer. However, we can use any numbers/variables that appear in the picture.

We know that BD and DC are BOTH equal to 1. Since AC equals 2, we know that AD equals 1 (since 2 - 1 = 1). Thus, triangle ABD is ISOSCELES.

We know one of the angles in triangle ABD (re: 120 degrees) and since that triangle is isosceles, the other two angles MUST be equal and total the missing 60 degrees in that triangle. Thus, those two angles are BOTH 30 degrees.

Final Answer: C

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Top
Post new topic Post Reply
• Page 1 of 1