小明家有一块长方形铁皮（如图），爸爸想利用这块铁皮做一个圆柱形的桶．为了不浪费铁皮，他应选择几号圆形铁皮做底面？为什么？（单位：dm）
直接写出得数×15=×2=×=×= 1×=×=×34=×=×=×=×=×=
计算． 1×4.8 2×3.5 2.3×1 2×0.63．
口算：×15=×2=×=×=×= 1×=×=×34=×=×=×=×=
直接写出得数．×40=﹣=×= 2×= 24×=×22= 18×=×=×=×=
计算下面各题×=×=×= 9××=+×××=
×15=
×2=
×
=
×
=
=
×
=
×34=
×
=
×
=
×
=
×
=
×
=
×4.8 2
×3.5 2.3×1
2
×0.63．
×15=
×2=
×
=
×
=
×
= 1×
=
×
=
×34=
×
=
×
=
×
=
×
=
×40=
﹣
=
×
= 2×
= 24×
=
×22= 18×
=
×
=
×
=
×
=
×
=
×
=
×
=
×
=
+
×
×
×
=
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