A,B,C,and D are on number line

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anant03: Senior | Next Rank: 100 Posts; Posts: 70; Joined: Tue Sep 01, 2015 7:48 am

by anant03 » Mon Sep 14, 2015 9:59 am

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Source: Beat The GMAT — Data Sufficiency | Mon Sep 14, 2015 9:59 am

GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Mon Sep 14, 2015 10:43 am

I posted a solution here:

https://www.beatthegmat.com/distance-bet ... 83096.html

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Max@Math Revolution: Elite Legendary Member; Posts: 3991; Joined: Fri Jul 24, 2015 2:28 amFollowed by: 37 members; Location: Las Vegas, USA; Thanked: 19 times

by Max@Math Revolution » Tue Sep 15, 2015 8:38 am

Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem.
Remember equal number of variables and independent equations ensures a solution.

The p[oints A, B, C and D are on a number line, not necessarily in that order. If the distance between A and B is 18 and the distance between C and D is 8, what is the distance between B and D?
1) The distance between C and A is the same as the distance between C and B
2) A is to the left of D on the number line

Transforming the original condition and the question, we have multiple variables since the position of A,B,C,D is not fixed. Since there is only 1 equation each in 1) and 2), there is high probability that E is the answer.
Using both 1) and 2), BD=1, 17 thus the answer is not unique. Therefore the answer is E.

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