Number Series, Coding and DecodingMCQPYQ Nov. 20Question 2166 of 217
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Which of the following is the odd one: 6,9,15,21,24,26,30\displaystyle 6, 9, 15, 21, 24, 26, 30.

Options

A24
B30
C26
D9
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Correct Answer

✅ Option c — 26

All Options:

  • A24
  • B30
  • C26
  • D9

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Detailed Solution & Explanation

Let's inspect the divisibility of the numbers in the series:
- 6=3×2\displaystyle 6 = 3 \times 2
- 9=3×3\displaystyle 9 = 3 \times 3
- 15=3×5\displaystyle 15 = 3 \times 5
- 21=3×7\displaystyle 21 = 3 \times 7
- 24=3×8\displaystyle 24 = 3 \times 8
- 30=3×10\displaystyle 30 = 3 \times 10

All the numbers in the series are multiples of 3\displaystyle 3, except 26\displaystyle 26, which is not divisible by 3\displaystyle 3 (26=3×8+2\displaystyle 26 = 3 \times 8 + 2).

Therefore, 26\displaystyle 26 is the odd man out.

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

About This Chapter: Number Series, Coding and Decoding

Paper

Paper 3: Quantitative Aptitude

Weightage

5 Marks

Key Topics

Number series, Coding & Decoding, Odd man out

This chapter covers Number series, Coding & Decoding, Odd man out and is part of Paper 3: Quantitative Aptitude in the CA Foundation exam.

View Official ICAI Syllabus

Exam Strategy Tip

This topic carries 5 Marks weightage. Focus on understanding core concepts rather than memorizing.

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