BukrsGmat wrote:

A man sets out to cycle from BBSR to CTC and at the same time another man starts from CTC to BBSR. After passing each other they complete their journeys in 4 and 9 hrs respectively. At what rate does the second man cycle if the first one cycles at 9 km/hr.

A. 4 km/hr

B. 6 km/hr

C. 8 km/hr

D. 9 km/hr

E. can't be determined

You can use the formula or the ratio approach.

Formula:

If two objects A and B start simultaneously from opposite points and, after meeting, reach their destinations in ‘a’ and ‘b’ hours respectively (i.e. A takes ‘a hrs’ to travel from the meeting point to his destination and B takes ‘b hrs’ to travel from the meeting point to his destination), then the ratio of their speeds is given by:

\(Sa/Sb = \sqrt{(b/a)} = \sqrt{9/4} = 3/2\)

So the ratio of speeds of first man and second man is 3:2

If the first man cycles at 9 km/hr (which is 3*3), the second will cycle at 2*3 = 6 km/hr

Check out another approach in this post (the question in the post uses almost same values):

http://www.veritasprep.com/blog/2013/04 ... -formulas/
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Veritas Prep GMAT Instructor

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