有一块正方形手帕,它的一条边长20厘米,要准备在这块手帕上镶一条漂亮的花边,应该准备多长的花边?
3÷ ==0.75=6: = %
3÷ ==0.6=6: = %.
3:5==9: == .
=0.375=12÷ = %=0.45= %= ÷ .
= ÷ = = % ÷ =0.25== %