（1/110*2.1*0.54*55）/54*0.21*4又1/2
=（55×1/110）×（0.54/54）×（2.1/0.21）×4.5
=1/2×0.01×10×4.5
=0.225抱歉是4又1/5（1/110*2.1*0.54*55）/54*0.21*4又1/5=（55×1/110）×（0.54/54）×（2.1/0.21）×4.2=1/2×0.01×10×4.2=0.21