设：半径为x则：x+2x+2xπ=46.4解得：x=5所以这个圆的面积=半径²π =5²π =25×3.14 =78.5平方分米希望帮到你！求采纳
3.14xrx2+2r+r=46.4 9.28r=46.4 r=5厘米3.14x5x5=78.5平方厘米
