i leave the calculator work to you.
7. diameter 4 miles, circumference 4π miles
8. radius 0.2 miles, circumference 0.4π miles
[this is a bad problem because the actual radius of a car on the track is less than 0.2 miles so the answer is less than 0.4π miles]
9. radius 6 feet, circumference 12π feet
10. diameter 14 cm, circumference 14π cm
11. diameter 4.8 feet, circumference 4.8π feet
the answer is a