涛涛gwd math1 q7 有关fraction的问题~

xyc19901015

A circular mat with diameter 20 inches is placed on a square tabletop, each of whose sides is 24 inches long.  Which of the following is closest to the fraction of the tabletop covered by the mat?

A.    5/12
B.    2/5
C.    1/2
D.    3/4
E.    5/6
这道题答案是C，这里求得fraction是指circular mat 占square的比例吗？请赐教，谢谢！