AMC8 1990

AMC8 1990 · Q18

AMC8 1990 · Q18. It mainly tests Basic counting (rules of product/sum), 3D geometry (volume).

Each corner of a rectangular prism is cut off. Two (of the eight) cuts are shown. How many edges does the new figure have?

一个长方体每个角都被切掉。图中展示了八个切口中的两个。新图形有多少条边？

(A) 24 24

(B) 30 30

(D) 42 42

(E) 48 48

Answer

Correct choice: (C)

正确答案：（C）

Solution

The original prism had 12 edges. Each "cut-off" corner yields 3 additional edges, so the new figure has a total of 12 + 8 x 3 = 36 edges.

原来有 12 条边。每个切角增加 3 条边，8×3=24，总共 12+24=36。

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