Multiple choice

Find a wrong number in the series: 7, 28, 63, 124, 215, 342, 511

  1. 7

  2. 28

  3. 124

  4. 215

  5. 342
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B Correct answer
Explanation

The series follows the pattern n^3 - 1: 2^3-1=7, 3^3-1=26 (not 28), 4^3-1=63, 5^3-1=124, 6^3-1=215, 7^3-1=342, 8^3-1=511. The wrong number is 28.

AI explanation

The pattern of the sequence is based on the cubes of natural numbers, but the given terms are one less than these cubes. We have 2^3 - 1 = 7, 3^3 - 1 = 26, 4^3 - 1 = 63, 5^3 - 1 = 124, 6^3 - 1 = 215 and 7^3 - 1 = 342. The second term should be 26 instead of 28, making 28 the wrong number.

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