What will be the (9)th term in the sequence (1,4,2,8,4,16,8,32,\ldots)?
Answer and explanation
Correct answer: 16
The terms at odd positions are 1, 2, 4, 8, 16, \ldots, so each successive odd-position term is double the previous one. The 9th position is odd and is the fifth term of this subsequence; hence the 9th term is 16. The value 64 is the 12th term, and may be chosen by incorrectly treating the entire sequence as a single doubling pattern. Exam tip: For such sequences, list the odd-position and even-position terms separately before identifying the rule.
Frequently asked questions
What is the correct answer to this question?
16
Why is this the correct answer?
The terms at odd positions are 1, 2, 4, 8, 16, \ldots, so each successive odd-position term is double the previous one. The 9th position is odd and is the fifth term of this subsequence; hence the 9th term is 16. The value 64 is the 12th term, and may be chosen by incorrectly treating the entire sequence as a single doubling pattern. Exam tip: For such sequences, list the odd-position and even-position terms separately before identifying the rule.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Sequences.
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