Answer: 18 inches
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Step-by-step explanation:
A point on the wheel travels 36pi inches when the wheel rotates one full cycle. This is the circumference of the circle.
C = 36pi
The formula for the circumference of a circle is C = pi*d where d is the diameter
C = pi*d
pi*d = C
pi*d = 36pi ... replace C with 36pi
d = 36pi/pi .... divide both sides by pi
d = 36
The diameter of the circle is 36, so half that is 18, which is the radius.