数学题：一块长方形薄钢板长2.4米、宽1米、重6千克，从上边剪下一块直径是80厘米的圆片，这块圆片的质量是多少千克？

数学题解答：在厚度一定的情况下，钢板的质量和钢板的面积有关，面积越大，质量越重。也就是说，质量和面积成正比例。所以就可以用方程来解答这道题。

设这块圆片质量为X千克。80厘米＝0.8米

X : [3.14×（0.8÷2）²]=6 : (2.4×1)

X=1.256

答：这块圆片的质量是1.256千克。

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