Bunuel wrote:
Three friends A, B and C decide to run around a circular track. They start at the same time, from the same point and run in the same direction. A is the quickest and when A finishes the first lap lap, C is as much behind B as B is behind A. When A completes 3 laps, C is at the exact same point on the circular track as B was when A finished the first lap. What could be the ratio of the speeds of A, B and C?
A. 6 : 5 : 3
B. 5 : 4 : 2
C. 4 : 3 : 2
D. 5 : 4 : 3
E. 3 : 2 : 1
Are You Up For the Challenge: 700 Level QuestionsYou can use the options to solve the question.
"when A finishes the first lap lap, C is as much behind B as B is behind A" So the difference between the speed of A and B is the same as difference between the speed of B and C. Hence options (A) and (B) are out.
As per option (E), when A completes 3 laps, C would have completed 1 lap and would be at starting point too. But that is not possible. So (E) is out.
Now, check for option (C):
When A completes 1 lap, B completes 3/4 (three quarters of circle) and C completes 2/4 (Half of circle).
When A completes 3 laps, B completes 9/4 (quarter of circle) and C completes 6/4 (Half of circle)
C is not at the same position as B was.
Answer (D)
Let's check anyway:
When A completes 1 lap, B completes 4/5 and C completes 3/5 .
When A completes 3 laps, B completes 12/5 and C completes 9/5
Since 9/5 is (1 + 4/5), C is at the same position as B was.
_________________
Karishma
Veritas Prep GMAT Instructor
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