2009 AMC 8 第 5 题
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所有题目均经美国数学协会（MAA）官方合法授权使用。
5.
一个数列以 、、 开始。数列的第四个数是前三个数之和，即 。同样地，第四个数之后的每个数都是它前面三个数之和。这个数列的第八个数是多少？
A sequence of numbers starts with and The fourth number of the sequence is the sum of the previous three numbers in the sequence: In the same way, every number after the fourth is the sum of the previous three numbers. What is the eighth number in the sequence?
答案：D
小提示：
一项一项地生成这个数列
Generate the sequence one term at a time.
大提示：
每个新项都是前面三项之和
Each new term is the sum of the previous three terms.
解答：
数列开始为 、、。
接下来的项为 、、、、。
所以正确答案是 D。
The sequence begins
The next terms are and
Thus, D is the correct answer.
其他年份的第 5 题
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