下午2点，小红在操场上插了根1米高的竹竿，量得竹竿的影长是0.8米，在同一时刻，小红量得一棵树的影长为2米，你能算出这棵树的实际高度吗？在同一时刻，小华也在操场上插了根3米长的竹竿，你知道这根竹竿的影长吗？

数学题解答：在同一时刻同一地区，物体的长度与影长的比值是一定的，它们成正比例关系。所以：

①解：设这棵树的实际高度是X米。

1：0.8＝X：2

算出X＝2.5

②解：设竹竿的影长是Y米。

1：0.8＝3：Y

算出Y＝2.4

问题得以解决。

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