Xiaohong wraps a rope around a big tree. After unrolling the rope, the length of the rope is measured to be 2.512 meters. What is the cross-sectional area of the big tree in square decimeters?
小红用绳子绕着一棵大树围一周，把绳子展开后量得绳子的长度是2.512米，这棵大树的横截面积是多少平方分米？
<result>50.24</result>