If there are cubes with a length of 1/2 how many cubes will fit inside this rectangular prism​

Alex drew a circle with right triangle prq inscribed in it, as shown below: the figure shows a circle with points p, q, and r on it forming an inscribed triangle. side pq is a chord through the center and angle r is a right angle. arc qr measures 80 degrees.

Acircle has a circumference of 7.850 units. what is its radius?

Fast! find the length of cu. the triangles are similar. show your work.