7.2x25x8.2的简便算法7.2x25x8.2=180*8.2=1476直接计算
7.2x25x8.2的简便算法=8x25x0.9x8.2=200x8.2x0.9=1640x0.9=1640-1640x0.1=1640-164=1640-200+36=1476
