Auto Racing: MPH, radar gun, lap time

Question
How do you figure out the miles per hour in racing?Like how fast they go.What equation would you do.

Answer
The distance around the track (Miles) divided by the lap time gives Miles per Second.  Multiply this number by 3600 gives AVERAGE miles per hour.  To get instantaineous speed at a certain point on the track you would have to measure directly with somthing like a radar gun......