DS - Line concept

This topic has expert replies
User avatar
Legendary Member
Posts: 1665
Joined: Thu Nov 03, 2011 7:04 pm
Thanked: 165 times
Followed by:70 members

DS - Line concept

by karthikpandian19 » Mon Jul 16, 2012 10:55 pm
Please refer attachment (as there was a problem uploading the image)
Attachments
Knewton    quiz_assignment    completed.png
Problem
Regards,
Karthik
The source of the questions that i post from JUNE 2013 is from KNEWTON

---If you find my post useful, click "Thank" :) :)---
---Never stop until cracking GMAT---
Source: — Data Sufficiency |

Junior | Next Rank: 30 Posts
Posts: 13
Joined: Tue Jul 17, 2012 12:43 am
Location: London
Thanked: 2 times
GMAT Score:760

by willrc » Tue Jul 17, 2012 1:19 am
This is a nice one.

Start with statement 2 as it's easier. ADE is an isosceles triangle (because AD=AE). If B and C are the midpoints of AD and FE we know that line m is parallel to line n. However, we don't know anything about line l. If you imagine a "hinge" at A, line l could tilt without affecting the constraints we've been given so far. INSUFFICIENT. That leaves A, C and E.

Statement 1 tells us that line l is parallel to the base of the triangle, because the exterior angles at A must be the same (it's isosceles). However, now we don't know about line m (it might not be parallel to the baseline n). INSUFFICIENT. That leaves C and E.

Together, they are sufficient, because we know l and m are both parallel to n and therefore to each other. Answer: C