Multiple choice

Find the missing number (?) in the series. $1, 1, 4, 8, 9, ?, 16, 64 ...$

  1. 21

  2. 23

  3. 25

  4. 27
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The series interleaves squares and cubes: squares at positions 1,3,5,7 (1,4,9,16) and cubes at positions 2,4,6,8 (1,8,?,64). The missing term is position 6, which should be 3³ = 27. Pattern: odd positions are n², even positions are n³.

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