Multiple choice

Directions: Given below is a series. Analyse the pattern of the series and answer the the question that follows. 15, 64, 185, 354, 643, x If 25% of x is the first term of a new series following the same pattern as the given one, then what is the third term of the new series?

  1. 396

  2. 412

  3. 421

  4. 690

  5. 386
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C Correct answer
Explanation

Series: 15, 64, 185, 354, 643. Differences: 49, 121, 169, 289. These are squares of 7, 11, 13, 17 (primes). Next difference is 19^2 = 361. x = 643 + 361 = 1004. 25% of x = 251. New series: 251, 300, 421 (following same prime-square differences: 49, 121).

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