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 660-mile journey? Assume that the train makes no intermediate stops.	Choose the correct choice from the following:
A) 8
B) 8.5
C) 11
D) 9.5
E) 10
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 660-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   7 70 280   8 80 360   9 90 450   10 100 550   11 110 660   It takes a total of nine hours to cover the 660 mile distance.   ANSWER: C. 11
<result>C</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 660-mile journey? Assume that the train makes no intermediate stops.