Abcd is a square.

what is the length of line segment dc?

5 units
7 units
11 units
13 units

It can be any of these. We cannot actually say without knowing the length of any of the other sides.

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

(c, 0) i might be wrong so don't put full faith on my answer