Multiple choice

Directions: Find the wrong term in the following number series. 18, 19.5, 41.5, 128, 513.5, 2588, 15534.5

  1. 41.5

  2. 513.5

  3. 2588

  4. 15334.5

  5. None of the above
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B Correct answer
Explanation

The intended pattern is multiply by successive integers and add successive half-integers: x1 + 1.5, x2 + 2.5, x3 + 3.5, and so on. After 128, the next term should be 128 x 4 + 4.5 = 516.5, so 513.5 is the wrong term. The later terms match the corrected pattern.

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