AMC8 2003

AMC8 2003 · Q18

AMC8 2003 · Q18. It mainly tests Graphs & networks (basic), Logic puzzles.

Each of the twenty dots on the graph below represents one of Sarah’s classmates. Classmates who are friends are connected with a line segment. For her birthday party, Sarah is inviting only the following: all of her friends and all of those classmates who are friends with at least one of her friends. How many classmates will not be invited to Sarah’s party?

下图中有二十个点，每个点代表 Sarah 的一位同学。朋友之间的同学用线段连接。Sarah 的生日派对只邀请以下人员：她所有的朋友以及所有与她的朋友至少有一个朋友的同学。有多少位同学不会被邀请到 Sarah 的派对？

(A) 1 1

(B) 4 4

(D) 6 6

(E) 7 7

Answer

Correct choice: (D)

正确答案：（D）

Solution

In the graph below, the six classmates who are not friends with Sarah or with one of Sarah’s friends are circled. Consequently, six classmates will not be invited to the party.

在下图中，圈出的六个同学既不是 Sarah 的朋友，也不是 Sarah 朋友的朋友。因此，有六个同学不会被邀请到派对。

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