8 full rotations measures 5 meters.
That means 8 times the circumference is 5 meters.
Let C = circumference.
8C = 5
C = 5/8 = 0.625
The circumference measures 0.625 m.
The circumference is
[tex] C = 2 \pi r[/tex]
Now we substitute our value into the circumference formula.
[tex]0.625 = 2 \pi r [/tex]
[tex]2 \pi r = 0.625 [/tex]
[tex]\pi r= 0.3125[/tex]
[tex]r = \dfrac{0.3125}{\pi} [/tex]
[tex]r \approx 0.09947 [/tex]
[tex]r \approx 0.1 ~m[/tex]