1998 AMC 8 第 18 题

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18.

如下图所示,一张长方形纸先从下往上折,再从左往右折,最后在 XX 处打一个孔。展开后纸是什么样子?

As indicated by the diagram below, a rectangular piece of paper is folded bottom to top, then left to right, and finally, a hole is punched at XX. What does the paper look like when unfolded?

答案:B
知识点:折纸反射(几何)
难度评级:1280
解答:

最后折好的长方形是原纸的右上四分之一,孔打在这个折后长方形的左上部分。

展开时,孔会分别关于水平和竖直折痕反射。只有选项 B 有这四个对应位置的孔。

所以正确答案是 B

The final folded rectangle is the upper-right quarter of the original sheet, and the hole is punched in the upper-left part of that folded rectangle.

Unfolding reflects the hole across the horizontal and vertical fold lines. Only choice B has the four corresponding holes.

Thus, the correct answer is B .

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