MBA Spotlight – The Biggest MBA Fair is June 13-14
close
It is currently 29 May 2023, 21:27
Register
GMAT Club Tests
Decision Tracker
My Rewards
New posts
New comers' posts

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

In quadrilateral ABCD above, what is the length of AB ?

15 posts Go to First Unread Post
Print view
NEW TOPIC
POST REPLY
Downloads
My Bookmarks
Reviews
SORT BY:
Date
Kudos
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 88716
CAT Tests Forum Quiz Mode Top Member of the Month
In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  26 Apr 2019, 01:38
2
Kudos
25
Bookmarks
Expert Reply
Quiz Dashboard Attempt only this question Same topic and source Same topic and difficulty Same source and difficulty Random Chronological Reverse chronological Learn more
00:00
A
B
C
D
E

Difficulty:

5% (low)

Question Stats:

87% (01:09) correct 13% (01:32) wrong based on 1662 sessions

Hide Show timer Statistics


In quadrilateral ABCD above, what is the length of AB ?


A. \(\sqrt{26}\)

B. \(2\sqrt{5}\)

C. \(2\sqrt{6}\)

D. \(3\sqrt{2}\)

E. \(3\sqrt{3}\)


PS58502.01
OG2020 NEW QUESTION

Show Spoiler
Attachment:
2019-04-26_1235.png
2019-04-26_1235.png [ 8.99 KiB | Viewed 29899 times ]
ShowHide Answer
Official Answer
Official Answer and Stats are available only to registered users. Register/Login.

_________________
New to the GMAT CLUB Forum?

My Signature Questions' Collection:


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics
Signature Read More
Quiz Dashboard Attempt only this question Same topic and source Same topic and difficulty Same source and difficulty Random Chronological Reverse chronological Learn more
Most Helpful Expert Reply
User avatar
L
BrentGMATPrepNow
GMAT Club Legend
GMAT Club Legend
Joined: 12 Sep 2015
Posts: 6911
Location: Canada
Top Member of the Month
In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  Updated on: 20 May 2020, 11:18
4
Kudos
3
Bookmarks
Expert Reply
Top Contributor
Bunuel wrote:

In quadrilateral ABCD above, what is the length of AB ?


A. \(\sqrt{26}\)

B. \(2\sqrt{5}\)

C. \(2\sqrt{6}\)

D. \(3\sqrt{2}\)

E. \(3\sqrt{3}\)


PS58502.01
OG2020 NEW QUESTION

Show Spoiler
Attachment:
2019-04-26_1235.png

First add a line to join B and D:



If we focus on the blue right triangle, we can EITHER recognize that legs of length 3 and 4 are part of the 3-4-5 Pythagorean triplet, OR we can apply the Pythagorean Theorem.

Either way, we'll see that the triangle's hypotenuse (BD) must have length 5

Now, when we focus on the red right triangle, we can . . .

. . . apply the Pythagorean Theorem to write: x² + 1² = 5²
Simplify: x² + 1 = 25
So: x² = 24
So: x = √24 = √[(4)(6)] = (√4)(√6) = 2√6

Answer: C

Cheers,
Brent
_________________
Brent Hanneson – Creator of gmatprepnow.com
I’ve spent the last 20 years helping students overcome their difficulties with GMAT math, and the biggest thing I’ve learned is…
Many students fail to maximize their quant score NOT because they lack the skills to solve certain questions but because they don’t understand what the GMAT is truly testing - Learn more
Signature Read More

Originally posted by BrentGMATPrepNow on 29 Apr 2019, 10:49.
Last edited by BrentGMATPrepNow on 20 May 2020, 11:18, edited 1 time in total.
General Discussion
User avatar
L
nick1816
DS Forum Moderator
Joined: 19 Oct 2018
Posts: 1897
Location: India
In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  Updated on: 05 Aug 2019, 15:31
1
Kudos
2
Bookmarks
Join D and B
DCB is an right angle triangle

\(DB^2= CD^2 +BC^2\)

\(DB^2=9 +16=25\)

\(or DB=5\)

Also, \(DB^2= AB^2 + AD^2\)

\(25=AB^2 + 1\)

\(AB^2 = 24\)

\(AB= 2\sqrt{6}\)

Originally posted by nick1816 on 26 Apr 2019, 02:11.
Last edited by nick1816 on 05 Aug 2019, 15:31, edited 2 times in total.
User avatar
L
Archit3110
GMAT Club Legend
GMAT Club Legend
Joined: 18 Aug 2017
Status:You learn more from failure than from success.
Posts: 7504
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE:Marketing (Energy and Utilities)
GMAT ToolKit User Reviews Badge
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  27 Apr 2019, 05:28
Bunuel wrote:

In quadrilateral ABCD above, what is the length of AB ?


A. \(\sqrt{26}\)

B. \(2\sqrt{5}\)

C. \(2\sqrt{6}\)

D. \(3\sqrt{2}\)

E. \(3\sqrt{3}\)


PS58502.01
OG2020 NEW QUESTION

Show Spoiler
Attachment:
2019-04-26_1235.png


join BD we get two ∆ right angled BCD and ABD ; BCD ; 3:4:5 and BD = 5 so 25-1 = AB^2
AB - \(2\sqrt{6}\)
IMO C
User avatar
L
EMPOWERgmatRichC
GMAT Club Legend
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21481
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  27 Apr 2019, 17:03
1
Kudos
Expert Reply
Hi All,

We're asked for the length of AB in quadrilateral ABCD.

When dealing with 'weird' shapes, it often helps to break the shape down into 'pieces' that are easier to deal with. Here, if you draw a line from B to D, you will from 2 RIGHT TRIANGLES.

Triangle BCD has legs of 3 and 4, so it's a 3/4/5 right triangle.
Triangle BAD then has a leg of 1 and a hypotenuse of 5. We can use the Pythagorean Formula to find the missing leg...

1^2 + B^2 = 5^2
1 + B^2 = 25
B^2 = 24

From here, if we square-root both sides, we'll have...
B = √24
B = 2√6

Final Answer:
Show Spoiler
C


GMAT assassins aren't born, they're made,
Rich
_________________
EMPOWERgmat.com
The Course Used By GMAT Club Moderators To Earn 750+
Try it for FREE Today!

souvik101990 Score: 760 Q50 V42 ★★★★★
ENGRTOMBA2018 Score: 750 Q49 V44 ★★★★★
Signature Read More
User avatar
L
EgmatQuantExpert
e-GMAT Representative
Joined: 04 Jan 2015
Posts: 3746
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  30 Apr 2019, 23:50
Expert Reply

Solution



Given:

    • AD= 1
    • CD=1
    • BC=1

To Find:
    • The length of AB.

Approach and Working:

Let us join the points B and D.



Since ∆ BCD is a right -angled triangle, we can apply Pythagoras theorem in ∆ BCD.
    • Thus, \(BD^2\) = \(CD^2\) +\(BC^2\)
      o \(BD^2\) = \(4^2\) +\(3^2\) = 16+9 = 25
      o \(BD^2\) = 25
         BD=5

Now, we can apply Pythagoras theorem in triangle ABD.
    • Hence, \(BD^2\) =\(AD^2\) + \(AB^2\)
      o 25 = 1 + \(AB^2\)
         \(AB^2\) = 24
         AB = √24 = 2√6.

Hence, option C is the correct answer.

Correct Answer: Option C
_________________
Free Trial: Get 25 AI powered videos | 400 practice questions | 8 free webinars

Case studies: How a personalized study plan can save you 60+ hours

MBA admits: M7 admits | INSEAD admits | ISB admits [40+ case studies]


Learn why e-GMAT has 10X more 700+ verified scores than other GMATClub partners – Read our 2000+ reviews
Signature Read More
User avatar
L
ScottTargetTestPrep
Target Test Prep Representative
Joined: 14 Oct 2015
Status:Founder & CEO
Affiliations: Target Test Prep
Posts: 17404
Location: United States (CA)
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  02 May 2019, 17:27
Expert Reply
Bunuel wrote:

In quadrilateral ABCD above, what is the length of AB ?


A. \(\sqrt{26}\)

B. \(2\sqrt{5}\)

C. \(2\sqrt{6}\)

D. \(3\sqrt{2}\)

E. \(3\sqrt{3}\)


PS58502.01
OG2020 NEW QUESTION

Show Spoiler
Attachment:
2019-04-26_1235.png


If we draw diagonal BD, we’ve created two right triangles: BCD and BAD. We see that triangle BCD is a 3-4-5 right triangle. So we see that side BD = 5.

Therefore, triangle BAD is a right triangle with a leg of 1 and a hypotenuse of 5. We can let side AB = n and use the Pythagorean theorem to determine n.

1^2 + n^2 = 5^2

1 + n^2 = 25

n^2 = 24

n = √24

n = √4 x √6 = 2√6

Answer: C
_________________
See why Target Test Prep is the top rated GMAT course on GMAT Club. Read Our Reviews
Signature Read More
avatar
B
Ashank07
Intern
Intern
Joined: 19 Jul 2017
Posts: 13
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  29 May 2019, 13:23
Bunuel wrote:

In quadrilateral ABCD above, what is the length of AB ?


A. \(\sqrt{26}\)

B. \(2\sqrt{5}\)

C. \(2\sqrt{6}\)

D. \(3\sqrt{2}\)

E. \(3\sqrt{3}\)


PS58502.01
OG2020 NEW QUESTION

Show Spoiler
Attachment:
2019-04-26_1235.png


If we draw diagonal BD, There are two right triangles: BCD and BAD. We see that triangle BCD is a 3-4-5 right triangle. So we see that side BD = 5.

Therefore, triangle BAD is a right triangle with a leg of 1 and a hypotenuse of 5. Now use the Pythagorean theorem to determine AB.

1^2 + AB^2 = 5^2

1 + AB^2 = 25

AB^2 = 24

AB = √24

AB = √4 x √6 = 2√6

Answer: C

avatar
S
Shrey9
Current Student
Joined: 23 Apr 2018
Posts: 133
Reviews Badge
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  05 Aug 2019, 08:28
HI,
can we also use the 30 : 60 : 90 triangle property to solve for the required side here ?

I tried using, but got a weird answer..
User avatar
L
EMPOWERgmatRichC
GMAT Club Legend
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21481
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  05 Aug 2019, 15:25
Expert Reply
Hi Shrey9,

Neither of these triangles is a 30/60/90 right triangle - so that property does not apply. To use 30/60/90 rules, you need to either have the 3 angles or know that you have a right triangle and 2 of the sides that fit the relationship of 2 of the 3 sides of that type of triangle (re. X : X√3 : 2X)

GMAT assassins aren't born, they're made,
Rich
_________________
EMPOWERgmat.com
The Course Used By GMAT Club Moderators To Earn 750+
Try it for FREE Today!

souvik101990 Score: 760 Q50 V42 ★★★★★
ENGRTOMBA2018 Score: 750 Q49 V44 ★★★★★
Signature Read More
avatar
S
Shrey9
Current Student
Joined: 23 Apr 2018
Posts: 133
Reviews Badge
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  05 Aug 2019, 15:45
1
Kudos
EMPOWERgmatRichC wrote:
Hi Shrey9,

Neither of these triangles is a 30/60/90 right triangle - so that property does not apply. To use 30/60/90 rules, you need to either have the 3 angles or know that you have a right triangle and 2 of the sides that fit the relationship of 2 of the 3 sides of that type of triangle (re. X : X√3 : 2X)

GMAT assassins aren't born, they're made,
Rich




so what you're saying is Pythagoras can be applied to any right triangle (even if its just one angle, which is 90deg) and 30 :60 : 90 or 45 : 45 : 90 can't just be applied when we don't know other angles apart from the 90 deg one ? (coz it could be 90 : 46 : 44 etc..)
User avatar
L
EMPOWERgmatRichC
GMAT Club Legend
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21481
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  05 Aug 2019, 19:48
Expert Reply
Hi Shrey9,

That is exactly correct! The Pythagorean Theorem applies to ANY Right Triangle; but the special Right Triangles only occur under specific conditions.

GMAT assassins aren't born, they're made,
Rich
_________________
EMPOWERgmat.com
The Course Used By GMAT Club Moderators To Earn 750+
Try it for FREE Today!

souvik101990 Score: 760 Q50 V42 ★★★★★
ENGRTOMBA2018 Score: 750 Q49 V44 ★★★★★
Signature Read More
User avatar
P
MHIKER
VP
VP
Joined: 14 Jul 2010
Status:No dream is too large, no dreamer is too small
Posts: 1053
In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  10 Dec 2020, 11:29
Top Contributor
Bunuel wrote:

In quadrilateral ABCD above, what is the length of AB ?


A. \(\sqrt{26}\)

B. \(2\sqrt{5}\)

C. \(2\sqrt{6}\)

D. \(3\sqrt{2}\)

E. \(3\sqrt{3}\)


PS58502.01
OG2020 NEW QUESTION

Show Spoiler
Attachment:
2019-04-26_1235.png


\(According \ to \ Pythagorean \ triples \ BD=5. \ (A 3:4:5) \ right \ triangle.\)

\((AB)^2+(1)^2=5^2\)

\((AB)^2=24\)

\(AB=\sqrt{24}\)

\(AB=\sqrt{6*4}\)

\(AB =2\sqrt{6}\)

The answer is \(C\)
_________________
Collections:-
PSof OG solved by GC members: https://gmatclub.com/forum/collection-ps-with-solution-from-gmatclub-110005.html
DS of OG solved by GC members: https://gmatclub.com/forum/collection-ds-with-solution-from-gmatclub-110004.html
100 GMAT PREP Quantitative collection https://gmatclub.com/forum/gmat-prep-problem-collections-114358.html
Collections of work/rate problems with solutions https://gmatclub.com/forum/collections-of-work-rate-problem-with-solutions-118919.html
Mixture problems in a file with best solutions: https://gmatclub.com/forum/mixture-problems-with-best-and-easy-solutions-all-together-124644.html
Signature Read More
User avatar
L
GMATinsight
GMAT Club Legend
GMAT Club Legend
Joined: 08 Jul 2010
Status:GMAT/GRE Tutor l Admission Consultant l On-Demand Course creator
Posts: 5859
Location: India
GMAT: QUANT EXPERT
Schools: IIM (A) ISB '24
GMAT 1: 750 Q51 V41
WE:Education (Education)
Reviews Badge
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  15 May 2021, 04:11
Expert Reply
Bunuel wrote:

In quadrilateral ABCD above, what is the length of AB ?


A. \(\sqrt{26}\)

B. \(2\sqrt{5}\)

C. \(2\sqrt{6}\)

D. \(3\sqrt{2}\)

E. \(3\sqrt{3}\)


PS58502.01
OG2020 NEW QUESTION

Show Spoiler
Attachment:
2019-04-26_1235.png



Wanna make solving the Official Questions interesting???


Click here and solve 1000+ Official Questions with Video solutions as Timed Sectional Tests
and Dedicated Data Sufficiency (DS) Course


Answer: Option C

Video solution by GMATinsight



Get TOPICWISE: Concept Videos | Practice Qns 100+ | Official Qns 50+ | 100% Video solution CLICK HERE.
Two MUST join YouTube channels : GMATinsight (1000+ FREE Videos) and GMATclub :)
_________________
GMATinsight
Great Results (Q≥50 and V≥40) l Honest and Effective Admission Support l 100% Satisfaction !!!
One-on-One GMAT Skype classes l On-demand Quant Courses and Pricing l Admissions Consulting
Call/mail: +91-9999687183 l info@gmatinsight.com (for FREE Demo class/consultation)
SUCCESS STORIES: From 620 to 760 l Q-42 to Q-49 in 40 days l 590 to 710 + Wharton l GMAT730+ESCP
FREE Resources: 22 FULL LENGTH TESTS l OG QUANT 50 Qn+VIDEO Sol. l NEW:QUANT REVISION Topicwise Quiz
Signature Read More
User avatar
D
avigutman
Tutor
Joined: 17 Jul 2019
Posts: 1294
Location: Canada
Schools: NYU Stern (WA)
GMAT 1: 780 Q51 V45
GMAT 2: 780 Q50 V47
GMAT 3: 770 Q50 V45
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink] New post  06 Apr 2022, 17:29
Expert Reply
Video solution from Quant Reasoning:
Subscribe for more: https://www.youtube.com/QuantReasoning? ... irmation=1

_________________
https://www.quantreasoning.com
Signature Read More
GMAT Club Bot
gmatclubot
Re: In quadrilateral ABCD above, what is the length of AB ? [#permalink]
06 Apr 2022, 17:29
NEW TOPIC
POST REPLY
Downloads
My Bookmarks
Reviews
Moderators:
Bunuel
Math Expert
88716 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3151 posts

cron

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions