Last visit was: 11 Sep 2026, 23:29 It is currently 11 Sep 2026, 23:29
Home
Messages
Tests
Schools
Events
Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
Back to Forum
Create Topic
Sub 505 (Easy)|   Geometry|      
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 11 Sep 2026
Posts: 113,472
Own Kudos:
840,751
Given Kudos: 111,474
Products:
GMAT Club Tests
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 113,472
Kudos: 840,751
If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is 14 Jul 2021, 01:30
Kudos
Add Kudos
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

5% (low)

Question Stats:

86% (00:53) correct 14% (01:19) wrong based on 80 sessions

History

Date
Time
Result
Not Attempted Yet

If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is the value of xº?

A. 40º
B. 50º
C. 65º
D. 80º
E. 100º

Show Spoiler
Attachment:
1.png
1.png [ 6.31 KiB | Viewed 2568 times ]
ShowHide Answer
Official Answer
B
User avatar
Showmeyaa
User avatar
Joined: 24 Jun 2019
Last visit: 08 Sep 2023
Posts: 427
Own Kudos:
538
 [1]
Given Kudos: 117
Location: India
Concentration: Marketing, Strategy
Products:
My Reviews
Posts: 427
Kudos: 538
 [1]
If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is 14 Jul 2021, 02:23
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel

If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is the value of xº?

A. 40º
B. 50º
C. 65º
D. 80º
E. 100º

Show Spoiler
Attachment:
1.png
Show more

In isos triangle BDC:
2x + 100 = 180
2x = 80
x = 40
So, DBC = 90 - 40 = 50
x = 50(Why? triangle BAD is isos)
IMO, (B)!
User avatar
rajatchopra1994
User avatar
Joined: 16 Feb 2015
Last visit: 22 Jun 2024
Posts: 1,052
Own Kudos:
1,344
Given Kudos: 30
Location: United States
Posts: 1,052
Kudos: 1,344
If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is 14 Jul 2021, 02:33
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Explanation:

In Triangle DBC,
DC=CB, Angle CDB = Angle DBC =y
Angle C = 100
Angle CDB + Angle DBC + Angle C = 180
2y + 100 = 180
y = 40
We know, Angle ABC is 90
Angle DBA = 90-40 = 50

Angle DBA = Angle DAB = 50

IMO-B

Posted from my mobile device
avatar
kantapong
avatar
Joined: 20 Jun 2021
Last visit: 06 Sep 2026
Posts: 107
Own Kudos:
225
 [1]
Given Kudos: 4
Posts: 107
Kudos: 225
 [1]
If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is 14 Jul 2021, 02:35
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
DAB = DBA = x
Triangle DCB has angles of 40, 40, 100.
So, x + 40 = 90 => x = 50 (B)
User avatar
asishron29181
User avatar
Joined: 04 May 2020
Last visit: 04 Nov 2022
Posts: 185
Own Kudos:
553
 [1]
Given Kudos: 68
Location: India
Schools: Great Lakes (I)
GMAT 1: 610 Q47 V27
WE:Programming (Computer Software)
Schools: Great Lakes (I)
GMAT 1: 610 Q47 V27
Posts: 185
Kudos: 553
 [1]
If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is 14 Jul 2021, 02:40
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is the value of xº

In triangle CBD,
CD = CB
angle CDB = angle CBD (isosceles triangle)
100 +2y = 180
2y = 80
y=40

In triangle ABD,
AD = BD
angle DAB = angle DBA
Also given
angle CBA = 90
angle DBA = 90 -40 =50
x = 50

IMO B
User avatar
sumitkrocks
User avatar
Joined: 02 Jul 2017
Last visit: 22 Aug 2023
Posts: 636
Own Kudos:
888
 [1]
Given Kudos: 333
Location: India
Concentration: Strategy, Technology
Schools: IIMA PGPX'22 ISB'22 NUS '23 ESADE IESE '24 NTU
GMAT 1: 730 Q50 V39
GMAT 2: 710 Q50 V36
Products:
My Reviews
Schools: IIMA PGPX'22 ISB'22 NUS '23 ESADE IESE '24 NTU
GMAT 2: 710 Q50 V36
Posts: 636
Kudos: 888
 [1]
If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is 14 Jul 2021, 03:00
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Two equal angles in Triangle BDC are \(\frac{(180-100)}{2} = 40\)
X= 90 - 40 = 50
Option B

Bunuel

If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is the value of xº?

A. 40º
B. 50º
C. 65º
D. 80º
E. 100º

Show Spoiler
Attachment:
1.png
Show more
User avatar
HarshaBujji
User avatar
Joined: 29 Jun 2020
Last visit: 11 Sep 2026
Posts: 731
Own Kudos:
941
 [1]
Given Kudos: 248
Location: India
Products:
My Reviews Forum Quiz
Posts: 731
Kudos: 941
 [1]
If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is 14 Jul 2021, 06:37
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel

If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is the value of xº?

A. 40º
B. 50º
C. 65º
D. 80º
E. 100º

Show Spoiler
Attachment:
The attachment 1.png is no longer available
Show more

Simply fill the angle to find x: IMO B

Follow the diagram
Attachments

PB07.PNG
PB07.PNG [ 8.23 KiB | Viewed 2211 times ]

User avatar
MathRevolution
User avatar
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Last visit: 27 Sep 2022
Posts: 10,057
Own Kudos:
20,406
Given Kudos: 4
GMAT 1: 760 Q51 V42
GPA: 3.82
Expert
Expert reply
GMAT 1: 760 Q51 V42
Posts: 10,057
Kudos: 20,406
If AD = DB, DC = CB, and angle ABC = 90º as shown above, then what is 14 Jul 2021, 10:08
Kudos
Add Kudos
Bookmarks
Bookmark this Post
In triangle DCB, since DC = CB, therefore angle CDB = angle CBD = 40 (sum of all angles in the traingle is 180)

Angle B is 90 hence and angle CBD is 40 so angle DBA is 90 - 40 = 50.

Since AD = DB, therefore angle DAB = angle DBA = 50 (angle opposite to equal sides are equal)

Therefore, x = 50

Answer B
Moderator:
Bunuel
Math Expert
113472 posts