GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 23 Jan 2019, 02:19

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.

Close

Request Expert Reply

Confirm Cancel
Events & Promotions in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
  • Key Strategies to Master GMAT SC

     January 26, 2019

     January 26, 2019

     07:00 AM PST

     09:00 AM PST

    Attend this webinar to learn how to leverage Meaning and Logic to solve the most challenging Sentence Correction Questions.
  • Free GMAT Number Properties Webinar

     January 27, 2019

     January 27, 2019

     07:00 AM PST

     09:00 AM PST

    Attend this webinar to learn a structured approach to solve 700+ Number Properties question in less than 2 minutes.

CD is parallel to EF. AD = DF, CD = 4, and DF = 3. What is EF ?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 52429
CD is parallel to EF. AD = DF, CD = 4, and DF = 3. What is EF ?  [#permalink]

Show Tags

New post 29 Oct 2017, 00:26
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

89% (01:34) correct 11% (01:46) wrong based on 51 sessions

HideShow timer Statistics

Image
CD is parallel to EF. AD = DF, CD = 4, and DF = 3. What is EF ?

(A) 4
(B) 5
(C) 6
(D) 7
(E) 8

Attachment:
2017-10-29_1225.png
2017-10-29_1225.png [ 5.54 KiB | Viewed 663 times ]

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Senior SC Moderator
avatar
V
Joined: 22 May 2016
Posts: 2368
CD is parallel to EF. AD = DF, CD = 4, and DF = 3. What is EF ?  [#permalink]

Show Tags

New post 29 Oct 2017, 08:23
Bunuel wrote:
Image
CD is parallel to EF. AD = DF, CD = 4, and DF = 3. What is EF ?

(A) 4
(B) 5
(C) 6
(D) 7
(E) 8

Attachment:
The attachment 2017-10-29_1225.png is no longer available

Attachment:
tri.png
tri.png [ 7.32 KiB | Viewed 521 times ]

Rotate the triangle clockwise 90 degrees.

∆ ACD is similar to triangle AEF:

Their bases (DC and FE) are parallel.

Those parallel lines are cut by transversals (sides AF and AE of the larger triangle).

∠ D = ∠F (corresponding)
∠ C = ∠E (corresponding)

Both triangles share ∠ A

By AAA, they are similar triangles, whose corresponding sides have the same ratio
Small side \(AD\) corresponds to large side \(AF\). Small side \(DC\) corresponds to large side \(EF\)

\(AD = 3\), \(CD = 4\)

For small ∆ ACD, \(\frac{side}{side} = \frac{AD}{DC}=\frac{3}{4}\)

That ratio will hold for larger ∆ AEF

\(AD = DF = 3\)
So side \(AF = 6\)
Let side \(EF = x\)

\((\frac{AD}{DC}=\frac{AF}{EF})=(\frac{3}{4}= \frac{6}{x})=\frac{6}{8}\)

\(EF = 8\)

Answer E
_________________

Life’s like a movie. Write your own ending.

Kermit the Frog

Intern
Intern
User avatar
B
Joined: 22 Jun 2017
Posts: 17
Location: Italy
GPA: 3.64
GMAT ToolKit User
CD is parallel to EF. AD = DF, CD = 4, and DF = 3. What is EF ?  [#permalink]

Show Tags

New post 31 Oct 2017, 07:34
Bunuel wrote:
Image
CD is parallel to EF. AD = DF, CD = 4, and DF = 3. What is EF ?

(A) 4
(B) 5
(C) 6
(D) 7
(E) 8

Attachment:
2017-10-29_1225.png


since AD=DF and CD is parallel to EF, CD is the midsegment of the triangle, and EF is equal 2 times the midsegment, so IMO the answer is E
GMAT Club Bot
CD is parallel to EF. AD = DF, CD = 4, and DF = 3. What is EF ? &nbs [#permalink] 31 Oct 2017, 07:34
Display posts from previous: Sort by

CD is parallel to EF. AD = DF, CD = 4, and DF = 3. What is EF ?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.