Answer:
a.
b.
Step-by-step explanation:
a. Radius of semicircle (r) = r
Diameter of semicircle (d) = 2r
Length of rectangle (l) = 2*diameter of semicircle = 2*2r = 4r
Distance around the track (p) = circumference of circle + 2(l)
Note: the two semicircles of the track = 1 full circle
Circumference of full circle = πd = π*2r = 2πr
Distance around the track:
p = 2πr + 2(4r)
p = 2πr + 8r
b. Rewriting the formula to make radius, r, the subject of the formula in terms of distance around the track.
Factor out r
Divide both sides by (2π + 8)