Safal wrote:

Sam and Chris leave City A for City B simultaneously at 6 A.M in the morning driving in two cars at speeds of 60 mph and 80 mph respectively. As soon as Chris reaches City B, he returns back to City A along the same route and meets Sam on the way back. If the distance between the two cities is 210 miles, how far from City A did Sam and Chris meet?

A.60 miles

B.120 miles

C.30 miles

D.180 miles

E.150 miles

You can use ratios to solve it easily.

Let's say, they meet x miles away from city A. Sam has covered a distance of x miles and Chris has covered a distance of 210 + (210 - x) = (420 - x) miles.

The speeds of Sam and Chris are in the ratio 60:80 i.e. 3:4. So in the same time, they will cover distance which will be in the ratio 3:4 too.

x/(420 - x) = 3/4

7x = 1260

x = 180 miles

Answer (D)

For more on ratios used in TSD, check:

http://www.veritasprep.com/blog/2011/03 ... os-in-tsd/
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Veritas Prep GMAT Instructor

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