15cm=0.15m
半径r=0.15/2=0.075m
圆面积:S=π*r^2=3.14*0.075^2
圆木体积:V=S*L=3.14*0.075^2*2.6=0.0459225m~0.046(立方米)
m:米 cm:厘米
明白吗?