A train traveled the first d miles of its journey it an average speed of 40 miles per hour, the next d miles of its journey at an average speed of y miles per hour, and the final d miles of its journey at an average speed of 160 miles per hour. If the train’s average speed over the total distance was 96 miles per hour, what is the value of y?  Choose the correct choice from the following:
A) 68
B) 84
C) 100
D) 120
E) 135
Average speed=Total distance traveled /Total time taken   3d/d/40+d/y+d/160=96   Solving for d and y,   15y=11y+480   4y=400   y=100   Answer 100
<result>C</result>
A train traveled the first d miles of its journey it an average speed of 40 miles per hour, the next d miles of its journey at an average speed of y miles per hour, and the final d miles of its journey at an average speed of 160 miles per hour. If the train’s average speed over the total distance was 96 miles per hour, what is the value of y?