如右图，将厚度为0.02厘米的纸在直径为10厘米的圆筒上卷成直径为20厘米的卷筒纸．请试着求出这卷纸的总长度．
算一算．+= 1﹣= ﹣= += ﹣= +=
修一条公路，第一队修了总长的，第二队修了总长的，两队共修了这条公路的几分之几？
计算下面各题．= = = ﹣= 1﹣=﹣= = ﹣= =
看谁算得又对又快．= = == = =．
3与4的倒数之差是多少？
+
= 1﹣
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﹣
= 
+
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﹣
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+
=
，第二队修了总长的
，两队共修了这条公路的几分之几？
= 
= 
= 
﹣
= 1﹣
=
﹣
= 
= 
﹣
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