AshikaP wrote:
Steve gets on the elevator at the 11th floor of a building and rides up at a rate of 57 floors per minute. At the same time Joyce gets on an elevator on the 51st floor of the same building and rides down at a rate of 63 floors per minute. If they continue traveling at these rates, at which floor will their paths cross?
A. 19
B. 28
C. 30
D. 32
E. 44
Even though this question uses elevators (which usually means a tougher question), it involves very simple relative speed calculation.
Steve is on 11th floor and Joyce on 51st floor so they have a distance of 40 floors between them.
Steve's speed is 57 floors/min and Joyce's speed is 63 floors/min in opposite direction (towards Steve).
Their relative speed will be the sum of their individual speeds = 57 + 63 = 120 floors/min
Time taken to meet = 40/120 = 1/3 min = 20 secs
Distance covered by Steve in 20 secs = Speed*Time = 57 * (1/3) = 19 floors.
So he is at 11+19 = 30th floor when they meet.
Answer (C)
Check this post on relative speed:
http://www.veritasprep.com/blog/2012/07 ... elatively/http://www.veritasprep.com/blog/2012/08 ... -concepts/ _________________
Karishma
Veritas Prep GMAT Instructor
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