1989 AMC 8 第 23 题

先试着解答 1989 AMC 8 第 23 题,然后核对你的答案与精心整理的解答,解答来自 LIVE by Po-Shen Loh。你也可以参加完整限时模拟考试、查看全部 1989 AMC 8 解答,或核对答案。

所有题目均经美国数学协会(MAA)官方合法授权使用。

23.

一位艺术家有 1414 个边长为 11 米的正方体。她把它们放在地面上,搭成如图所示的雕塑,然后给雕塑露出的表面上漆。她一共要漆多少平方米?
An artist has 1414 cubes, each with an edge of 11 meter. She stands them on the ground to form a sculpture as shown. She then paints the exposed surface of the sculpture. How many square meters does she paint?
2121
2424
3333
3737
4242
答案:C
知识点:表面积正方体
小提示:
分别数四个竖直侧面的露出面积,再加上从上方看到的面积
Count the exposed faces on the four vertical sides, then the faces seen from directly above
大提示:
每个侧面看到的阶梯面积是 66,上表面的投影覆盖整个 3×33 \times 3 底面
Each of the four sides shows 66 exposed faces, and looking straight down covers the full 3×33 \times 3 footprint of top faces
解答:
因为每一层都靠齐在同一个角上,所以从每个竖直方向看,露出的阶梯侧面都是 3+2+1=63 + 2 + 1 = 6 个小正方形面,四个方向共 4×6=244 \times 6 = 24 个侧面。
从上方看,露出的顶面覆盖整个 3×33 \times 3 的底面投影,所以顶面积是 99 平方米。底面不漆,因此总上漆面积是 24+9=3324 + 9 = 33 平方米。
所以正确答案是 C。
Because each higher layer is flush into one corner, each of the four vertical sides shows a stepped profile of 3+2+1=63 + 2 + 1 = 6 exposed square faces, for 4×6=244 \times 6 = 24 side faces.
Viewed from directly above, the top faces cover the full 3×33 \times 3 footprint, adding 99 more faces. The bottom rests on the ground and is not painted, so the total is 24+9=3324 + 9 = 33 square meters.
Thus, the correct answer is C .
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