体积=πX半径的平方X长度=3.14X(0.3/2)X(0.3/2)X100=7.07立方厘米铁的比重=7.8克/立方厘米 7.8克X7.07立方厘米=55克,0.055公斤或2市两多点
首先你要知道铁丝是圆的长柱体，体积V=π*D*D*L/4=3.14*0.003*0.003/4=0.007065L，已知铁的密度为7.85kg/L，m=0.007065*7.85=0.055107kg
