用彩带纸沿文具盒的表面围一周，彩带纸至少要多长？先估一估，再剪一段彩带纸试试．
（+）++++﹣+．
用你认为简便的方法计算．．
+=﹣=+=+= 1﹣=+=﹣+=++=
0.5+．
直接写出计算结果．+=+=+== 1﹣==
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．
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=
﹣
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﹣
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= 1﹣
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