Four circles make up a circle, and the diameter of each circle is 48.5. If you take the largest circle in the middle, what is the diameter of this circle? Beg the math emperor!
Idea: The centers of four circles are connected to form a square with a side length of 48.5. Find the length of the diagonal, and then subtract two radii, which is the diameter of the largest circle in the middle.
2*48.5*48.5=4704.5
4704.5^( 1/2)=68.6
68.6-48.5=20. 1