长方形的长是8cm,宽是5cm,求周长(5十8)X2=26cm
计算过程如下:[(0.5+0.8)×2.1/2+1.5×0.8]×22.89=(1.3×1.05+1.5×0.8)×22.89=(1.365+1.2)×22.89=2.565×22.89=58.71285