A train travels at the rate of 10 miles/hr for the first hour of a trip, at 20 miles/hr for the second hour, at 30 miles/hr for the third hour and so on. How many hours will it take the train to complete a 210-mile journey? Assume that the train makes no intermediate stops.  Choose the correct choice from the following options:
A) 6
B) 6.5
C) 7
D) 7.5
E) 5
A train travels at the rate of 10 miles/hr for the first hour of a trip, at 20 miles/hr for the second hour, at 30 miles/hr for the third hour and so on. How many hours will it take the train to complete a 210-mile journey? Assume that the train makes no intermediate stops.   I think the easiest way to solve this problem would be simply to count the number of miles it travels per hour (and in total)   Hour miles/hour Total miles   1 10 10   2 20 30   3 30 60   4 40 100   5 50 150   6 60 210   It takes a total of nine hours to cover the 210 mile distance.   6NSWER: 6 6
<result>A</result>
A train travels at the rate of 10 miles/hr for the first hour of a trip, at 20 miles/hr for the second hour, at 30 miles/hr for the third hour and so on. How many hours will it take the train to complete a 210-mile journey? Assume that the train makes no intermediate stops.