Answer:
about 37.7 feet
Step-by-step explanation:
If the outside wheels are turning twice as fast, they go twice the distance in the same time. The distance they travel is proportional to the radius of the circle, so the outside circle must have twice the radius of the inside circle.
Adding 6 ft to the radius of the inside circle doubles the radius, so the inside circle's radius must be 6 feet. Then the circumference of the inside circle is ...
C = 2πr = 2π(6 ft) = 12π ft ≈ 37.7 ft
