数学题:把一根长30cm，底面半径是8cm的圆木平均锯成4段，每段仍是圆柱体，锯成后的表面积比原来增加多少平方分米(得数保留两位小数）

数学题解答：先弄清一个问题：锯成四段，需要锯几次？

答案是3次。而每锯一次，就会多出2个底面，所以一个多出6个底面。3×2=6（个）

增加的表面积，就是用一个底面积去乘6，算式为：3.14 × 8² × 6 = 1205.76（平方厘米）=12.0576（平方分米）≈12.06（平方分米）

答：锯成后的表面积比原来增加12.06平方分米。

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