Number Series, Coding, Odd Man OutMTP Nov. 20Question 2183 of 217
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Find odd man out of the series 145,197,257,325,399\displaystyle 145, 197, 257, 325, 399

Options

A145\displaystyle 145
B399\displaystyle 399
C257\displaystyle 257
D325\displaystyle 325
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Correct Answer

✅ Option b — 399\displaystyle 399

All Options:

  • A145\displaystyle 145
  • B399\displaystyle 399
  • C257\displaystyle 257
  • D325\displaystyle 325

Detailed Solution & Explanation

Let's analyze the mathematical structure of the terms in the series: 145,197,257,325,399\displaystyle 145, 197, 257, 325, 399.
Each correct term follows the pattern n2+1\displaystyle n^2 + 1 for consecutive even numbers n\displaystyle n starting from 12\displaystyle 12:
- For n=12\displaystyle n = 12: 122+1=144+1=145\displaystyle 12^2 + 1 = 144 + 1 = 145
- For n=14\displaystyle n = 14: 142+1=196+1=197\displaystyle 14^2 + 1 = 196 + 1 = 197
- For n=16\displaystyle n = 16: 162+1=256+1=257\displaystyle 16^2 + 1 = 256 + 1 = 257
- For n=18\displaystyle n = 18: 182+1=324+1=325\displaystyle 18^2 + 1 = 324 + 1 = 325
- For n=20\displaystyle n = 20: 202+1=400+1=401\displaystyle 20^2 + 1 = 400 + 1 = 401 (the series lists 399\displaystyle 399, which is 202−1\displaystyle 20^2 - 1)

Since 399\displaystyle 399 violates the n2+1\displaystyle n^2 + 1 pattern, it is the odd man out.

Hence, **Option B** is the correct answer.

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