Look at this series: 21, 9, 21, 11, 21, 13, 21, ... What number should come…
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Look at this series: 21, 9, 21, 11, 21, 13, 21, ... What number should come next?
- A.
14
- B.
15
- C.
21
- D.
23
Attempted by 1890 students.
Show answer & explanation
Correct answer: B
Answer: 15
Explanation:
Look at the sequence: 21, 9, 21, 11, 21, 13, 21, ...
The sequence alternates between two subsequences:
Terms in odd positions (1, 3, 5, 7, ...): 21, 21, 21, 21 — always 21.
Terms in even positions (2, 4, 6, 8, ...): 9, 11, 13, ... — start at 9 and increase by 2 each time.
The next term is an even-position term following 13, so it is 15.