在右面正方形中画出一个最大的圆；测量出相关数据（标在图上），再求这个圆的周长．
直接得数．×21=×= 15÷=÷ 1﹣65%= 1+65%=÷=×=
直接写得数．×=×=×=×2= 5﹣= 12×= 1÷=+×=（6+）×=×39×=
口算下面各题．÷8=×= 5÷= 3+3÷7=×15= 10÷10%= 28×75%=×8×=
直接写出得数．×16=+= 0÷=÷3=÷= 7﹣=×= 8÷=
直接写出得数． 6÷=×= 0÷= 4.1﹣÷=﹣=÷=×8×=化简比0.6：=
×21=
×
= 15÷
=
÷
÷
=
×
=
×
=
×
=
×
=
=
= 1÷
=
+
×
=（6+
）×
×39×
=
÷8=
×
= 5÷
= 3+3÷7=
×15= 10÷10%= 28×75%=
×8×
=
×16=
+
= 0÷
=
÷3=
÷
= 7﹣
=
×
= 8÷
=
=
×
= 0÷
= 4.1﹣
÷
=
÷
=
×8×
=化简比0.6：
=
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