Question

正方形中有多少比例的面积被涂色？

What fraction of the square is shaded?

$\dfrac{1}{3}$

$\dfrac{2}{5}$

$\dfrac{5}{12}$

$\dfrac{3}{7}$

$\dfrac{1}{2}$

答案：E

知识点：面积对称性

难度评级：730

解答：

从一个顶点到对角顶点的对角线把正方形分成两个面积相等的部分。对角线一侧的每个涂色部分，都是另一侧某个等面积未涂色部分的镜像。

因此涂色面积和未涂色面积相等，正好有 $\dfrac12$ 的正方形被涂色。

所以正确答案是 E。

The diagonal from one corner to the opposite corner splits the square into two equal halves. Every shaded piece on one side of the diagonal is the mirror image of an equal unshaded piece on the other side.

So the shaded and unshaded areas are equal, and exactly $\dfrac12$ of the square is shaded.

Thus, the correct answer is E .

1990 AMC 8 第 3 题

答案：E

难度评级：730

解答：

其他年份的第 3 题