Multiple choice

Directions: Find the missing number in the following series. 1, 9, 36, 100, 225, ?

  1. 400

  2. 441

  3. 484

  4. 529
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B Correct answer
Explanation

The series is 1^2, 3^2, 6^2, 10^2, 15^2. The bases are 1, 3, 6, 10, 15. The differences between bases are 2, 3, 4, 5. The next base is 15 + 6 = 21. 21^2 = 441.

AI explanation

This series is formed by squaring consecutive triangular numbers. The numbers are derived from the squares of 1, 3, 6, 10, 15 and 21. The square of 21 is 441, which is the missing number.

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