A, B, K start from the same place and travel in the same direction at speeds of 30 km/hr, 40 km/hr, 120 km/hr respectively. B starts two hours after A. If B and K overtake A at the same instant, how many hours after A did K start?  Choose the correct choice from the following answers:  A) 3  B) 4  C) 6  D) 8  E) 10
In 2 hours, A travels 60 km.   B can catch A at a rate of 10 km/hr, so B catches A 6 hours after B starts.   So A and B both travel a distance of 240 km.   C needs 2 hours to travel 240 km, so C leaves 6 hours after A.   The answer is 6.
<result>C</result>
A, B, K start from the same place and travel in the same direction at speeds of 30 km/hr, 40 km/hr, 120 km/hr respectively. B starts two hours after A. If B and K overtake A at the same instant, how many hours after A did K start?