AMC8 1990
AMC8 1990 · Q3
AMC8 1990 · Q3. It mainly tests Area & perimeter.
What fraction of the square is shaded?
正方形中有多少分数被涂黑？
(A)
\frac{1}{3}
\frac{1}{3}
(B)
\frac{2}{5}
\frac{2}{5}
(C)
\frac{5}{12}
\frac{5}{12}
(D)
\frac{3}{7}
\frac{3}{7}
(E)
\frac{1}{2}
\frac{1}{2}
Answer
Correct choice: (E)
正确答案：（E）
Solution
Each shaded piece above or below the diagonal is matched by an identical unshaded piece meaning $\frac{1}{2}$ of the total area is shaded.
对角线上方或下方的每个涂黑部分都有一个相同的未涂黑部分与之匹配，这意味着总面积的 $\frac{1}{2}$ 被涂黑。
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