AMC8 1998
AMC8 1998 · Q22
AMC8 1998 · Q22. It mainly tests Patterns & sequences (misc).
Terri produces a sequence ... starts with positive integer, rules: <10 *9; even>9 /2; odd>9 -5. Sequence begins 98,49,... find 98th term.
Terri 生成一个序列……从正整数开始，规则：<10 *9；偶数>9 /2；奇数>9 -5。序列从 98,49,... 开始，求第 98 项。
(A)
6
6
(B)
11
11
(C)
22
22
(D)
27
27
(E)
54
54
Answer
Correct choice: (D)
正确答案：（D）
Solution
Answer (D): The sequence is 98, 49, 44, 22, 11, 6, 54, 27, 22, . . . . After 3 terms the cycle (22, 11, 6, 54, 27) is repeated. The 98th term is the fifth term of the cycle, and this is 27.
答案（D）：数列为 98，49，44，22，11，6，54，27，22，…… 在前 3 项之后，循环（22，11，6，54，27）重复出现。第 98 项是该循环的第 5 项，因此为 27。
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