Question

桌上放着五张卡片。每张卡片一面有一个字母，另一面有一个整数。可见的面显示 $P$ 、 $Q$ 、 $3$ 、 $4$ 和 $6$ 。Jane 说：“如果任意一张卡片的一面是元音字母，那么另一面就是偶数。”Mary 翻开一张卡片，证明 Jane 错了。Mary 翻开的是哪张卡片？

Five cards are lying on a table. Each card has a letter on one side and a whole number on the other side. The visible faces show $P,$ $Q,$ $3,$ $4,$ and $6.$ Jane said, "If a vowel is on one side of any card, then an even number is on the other side." Mary showed Jane was wrong by turning over one card. Which card did Mary turn over?

$3$

$4$

$6$

$P$

$Q$

答案：A

知识点：逻辑推理反例

难度评级：1140

解答：

要证明“元音字母必对应偶数”这个规则是错的，Mary 需要找到一张一面是元音字母、另一面是奇数的卡片。没有卡片显示元音字母，因为 $P$ 和 $Q$ 是辅音。

唯一显示奇数的卡片是 $3$ 。翻开它后露出元音字母，就会反驳 Jane 的说法。

所以正确答案是 A。

To show the rule "a vowel forces an even number" is false, Mary needs a card with a vowel on one side and an odd number on the other. No card shows a vowel, since $P$ and $Q$ are consonants.

The only card showing an odd number is $3.$ Turning it over reveals a vowel, which contradicts Jane's claim.

Thus, the correct answer is A .

1985 AMC 8 第 25 题

答案：A

难度评级：1140

解答：

其他年份的第 25 题