Forum Home > GMAT > Quantitative > Problem Solving (PS)
Events & Promotions
|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Dec 1310:00 AM EST
-12:00 PM EST
Have you ever wondered how to score a PERFECT 805 on the GMAT? Meet Julia, a banking professional who used the Target Test Prep course to achieve this incredible feat. Julia's story is nothing short of an inspiration.
Dec 1207:30 AM PST
-08:30 AM PST
Join the conversation to learn more about INSEAD vs LBS
Dec 1410:00 AM EST
-12:00 PM EST
Think a 100% GMAT Verbal score is out of your reach? Target Test Prep will make you think again! Our course uses techniques such as topical study and spaced repetition to maximize knowledge retention and make studying simple and fun.
Dec 1411:00 AM IST
-01:00 PM IST
Attend this session to learn how to Deconstruct arguments, Pre-Think Author’s Assumptions, and apply Negation Test.- Dec 15
11:00 AM IST
-01:00 PM IST
Attend this free GMAT Algebra Webinar and learn how to master the most challenging Inequalities and Absolute Value problems with ease. - Dec 16
08:00 AM PST
-11:59 PM PST
GMAT Club 12 Days of Christmas is a 4th Annual GMAT Club Winter Competition based on solving questions. This is the Winter GMAT competition on GMAT Club with an amazing opportunity to win over $40,000 worth of prizes! - Dec 17
09:00 AM PST
-10:00 AM PST
Join Manhattan Prep instructor Whitney Garner for a fun—and thorough—review of logic-based (non-math) problems, with a particular emphasis on Data Sufficiency and Two-Parts. - Dec 18
10:00 AM PST
-11:00 AM PST
Here is the essential guide to securing scholarships as an MBA student! In this video, we explore the various types of scholarships available, including need-based and merit-based options.
14 Dec 2021, 11:31
Kudos
Bookmarks
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
69% (02:17) correct
31%
(03:10)
wrong
based on 49
sessions
History
Date
Time
Result
Not Attempted Yet
In diagram above, ABCD is a rectangle, AD = 10, and AE = 5. What is the length of EC?
(A) 5√3
(B) 10
(C) 15
(D) 25
(E) 25√3
14 Dec 2021, 18:11
Kudos
Bookmarks
BrentGMATPrepNow
In diagram above, ABCD is a rectangle, AD = 10, and AE = 5. What is the length of EC?
(A) 5√3
(B) 10
(C) 15
(D) 25
(E) 25√3
Key property: The diagrams in GMAT problem solving questions are DRAWN TO SCALE unless stated otherwise.
If AE has length 5. . . .
. . . we can visually estimate additional lengths of 5 from E to C:
So, it looks like the length of EC is approximately 15.
When we check the answer choices, only answer choice C is close to our estimated length.
Answer: C
Aside: On test day, you can hold your finger to the monitor and use your marker to copy the length of AE on your finger. Then determine how many of those lengths fit into line segment EC.
---------------------------------------------------------------
APPROACH #2: Apply triangle properties
Let's first focus on RIGHT triangle AED below:
Since the hypotenuse (AD) is twice the length of leg AE, we know that triangle AED is a special 30-60-90 right triangle, which means ∠ADE = 30° and ∠DAE = 60°
Now, when we focus on RIGHT triangle ADC...
...we can see that ∠DCA = 30°.
Since we have another special 30-60-90 right triangle, we know that the hypotenuse will be twice the length of the side opposite the 30° angle (aka side AD).
This means the hypotenuse (AC) must have length 20.
Since AE + EC = AC, we can substitute values to get: 5 + EC = 20, which means EC = 15
Answer: C
