数学题：如图，正方形边长10厘米，两个直角梯形的高相等，面积相差10平方厘米，求X的长度是多少厘米？

数学题解答：

为便于区分，这两个梯形分别称为“左梯形”、“右梯形”。两个梯形的高都是5厘米，左梯形与右梯形有一条边重合（左梯形的上底，也是右梯形的下底），所以两个梯形上下底之和相差的正好就是x。

设左梯形上下底之和为a。根据“面积相差10平方厘米”列出方程：

a×5÷2 – (a-x)×5÷2 = 10

[a - (a - x)]×5÷2 = 10

x×5÷2 = 10

x=4

答：x的长度是4厘米。

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