Let P1, P2, P3, P4, P5, and P6 be six parabolas in the plane, each congruent to the parabola y=x2/16. The vertices of the six parabolas are evenly spaced around a circle. The parabolas open outward with their axes being extensions of six of the circle's radii. Parabola P1 is tangent to P2, which is tangent to P3, which is tangent to P4, which is tangent to P5, which is tangent to P6, which is tangent to P1. What is the diameter of the circle? conicsparabolaMath Prize for Girls