Number Series, Coding, Odd Man OutMTP Apr 21Question 2186 of 217
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Find odd man out of the following series 15,21,63,81,69\displaystyle 15, 21, 63, 81, 69

Options

A15\displaystyle 15
B21\displaystyle 21
C63\displaystyle 63
D81\displaystyle 81
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Correct Answer

✅ Option d — 81\displaystyle 81

All Options:

  • A15\displaystyle 15
  • B21\displaystyle 21
  • C63\displaystyle 63
  • D81\displaystyle 81

Detailed Solution & Explanation

Let's analyze the numbers in the series 15,21,63,81,69\displaystyle 15, 21, 63, 81, 69:
- All the numbers are composite numbers divisible by 3\displaystyle 3:
15=3×515 = 3 \times 5
21=3×721 = 3 \times 7
63=3×2163 = 3 \times 21
81=3×2781 = 3 \times 27
69=3×2369 = 3 \times 23
- However, 81\displaystyle 81 is a perfect square (81=92\displaystyle 81 = 9^2), whereas all the other numbers (15,21,63,69\displaystyle 15, 21, 63, 69) are not perfect squares.

Therefore, 81\displaystyle 81 is the odd man out.

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

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