cv3t3l1na wrote:

Carol started from home on trip averaging 30 miles per hour. How fast must her mother drive to catch up her in 3 hours if she leaves 30 minutes after Carol?

A. 35 m.p.h

B. 39 m.p.h

C. 40 m.p.h

D. 55 m.p.h

E. 60 m.p.h

It is a simple one, but the answer i get is 36. Maybe my calculation is wrong...

Speed of Carol = 30 mph

In 30 minutes Carol travels = 30 * (30/60) = 15 miles

Let the speed of carol's mother = V

So relative speed of Carol's mother w.r.t carol = V-30

Relative distance to be covered by Carol's mother in 3 hours = 15 miles with a relative speed of (V-30) mph

So, 15/(V-30) = 3

V = 35 mph

Answer A
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