1x2=2(dm)2x3.14=6.28(dm)1+1=2(dm)2x4=8(dm)8+6.28=14.28(dm)答：至少需要铁丝14.28dm.
1dm=10cm 10*2*3.14=6.28cm 10+10=20cm 20*4=80 cm 80+6.28=142.8cm
(4+3.14)dm
3.15dm
