2003 AMC 12A 第 13 题

先试着解答 2003 AMC 12A 第 13 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 2003 AMC 12A 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。

13.

图中实线围成的多边形由 44 个全等正方形边对边连接而成。再把一个全等正方形接到图中标出的九个位置之一的某条边上。九种所得多边形中,有多少种可以折成一个缺少一个面的立方体?

The polygon enclosed by the solid lines in the figure consists of 44 congruent squares joined edge-to-edge. One more congruent square is attached to an edge at one of the nine positions indicated. How many of the nine resulting polygons can be folded to form a cube with one face missing?

22

33

44

55

66

答案:E
知识点:展开图(立体几何)正方体
难度评级:1530
解答:

缺少一个面的立方体有 55 个面,所以第五个正方形必须折到四正方形拼块尚未占据的面上。追踪每个连接位置折到的面可知,位置 1,1, 2,2,33 会折到已占据的面并与之重叠。位置 4,4, 5,5, 6,6, 7,7, 8,8,99 都会折到未占据的面。因此九个位置中有 66 个可行。

所以正确答案是 E

A cube missing one face has 55 faces, so the fifth square must fold onto a face not already occupied by the four-square piece. Tracing the face reached by each attachment, positions 1,1, 2,2, and 33 fold onto a face already occupied and overlap it. Each of positions 4,4, 5,5, 6,6, 7,7, 8,8, and 99 folds onto an unoccupied face. Therefore 66 of the nine positions work.

Thus, the correct answer is E.

← 第 12 题#12
完整试卷

其他年份的第 13 题