AMC 8 1991 Problem 16
AMC8 1991 年第 16 题
变换与对称★★★☆☆
The 16 squares on a piece of paper are numbered as shown in the diagram. While lying on a table, the paper is folded in half four times in the following sequence:
(1) fold the top half over the bottom half
(2) fold the bottom half over the top half
(3) fold the right half over the left half
(4) fold the left half over the right half.
Which numbered square is on top after step 4 ?
一张纸上的 16 个方格如图所示编号。纸张平放在桌上，按以下顺序对折四次：
(1) 将上半部分向下对折
(2) 将下半部分向上对折
(3) 将右半部分向左对折
(4) 将左半部分向右对折。
第 4 步之后，哪个编号的方格在最上面？
- A.1
- B.9
- C.10
- D.14
- E.16
正确答案 · Correct Answer
B
解析 · Solution
Solution 1
Suppose we undo each of the four folds, considering just the top square until we completely unfold the paper. will be marked in the square if the face that shows after all the folds is face up, if that face is facing down.
Step 0: Step 1: Step 2: Step 3: Step 4: The marked square is in the same spot as the number .
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