10 minutes after a plane leaves the airport, it is reported to be 40 miles away. What is the average speed in miles per hour of the plane?
A
560
B
660
C
400
D
240
Correct Answer: 240
Hints: Average speed = 40 miles /10 min = 40 miles /(10/60) hrs = (40× 60)/ 10 mph = 240 mph