一张圆桌面要用铁皮条围成一圈，用来加固桌面．圆桌面的半径是1.2米，至少需要多长的铁皮条？（π取3.14）
直接写出得数．= = 1﹣=4﹣= = == =
计算下面各题．．
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++﹣+﹣+﹣．
1﹣．
= 
= 1﹣
=
= 
= 
=
= 
=
．
=
=
=
=
=
=
=
=
=
+
+
﹣
+
﹣
+
﹣
．
．
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