用一根铁丝围成一个直径是16厘米的圆，如果用它围成一个正方形，这个正方形的边长是多少厘米？
计算下面各题． ．
= × ==．
口算显身手．×2=×== 12﹣=×= 1×=×0= 3×=×=
口算题．×12=×= 60×=×=
．
= × =
=
．
×2=
×
=
=
=
×
= 1×
=
×0= 3×
=
×
=
×12=
×
=
=
×
=
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