We have two circles. One circle has a diameter of 12 cm's while another is D cm's. The circle with the diameter of 12 cm's fits inside the other circle. If rolled within the larger circle, the smaller circle rotates three times before coming back to rest at the same starting point. That is, Point p in the smaller circle starts and stop at Point P' on the larger circle after three revolutions.
What is the diameter of the bigger circle?