Number Series, Coding and DecodingMCQMTP May 20Question 2182 of 217
All Questions

Find the wrong term of the series 121,143,165,186,209\displaystyle 121, 143, 165, 186, 209

Options

A143\displaystyle 143
B165\displaystyle 165
C186\displaystyle 186
D209\displaystyle 209
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Correct Answer

✅ Option c — 186\displaystyle 186

All Options:

  • A143\displaystyle 143
  • B165\displaystyle 165
  • C186\displaystyle 186
  • D209\displaystyle 209

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Detailed Solution & Explanation

Let's calculate the differences between consecutive terms in the series:
- 143−121=22\displaystyle 143 - 121 = 22
- 165−143=22\displaystyle 165 - 143 = 22
- If the pattern of a constant difference of +22\displaystyle +22 continues:
- The next term should be 165+22=187\displaystyle 165 + 22 = 187.
- The term after that should be 187+22=209\displaystyle 187 + 22 = 209 (which is correct).

The series should form an arithmetic progression: 121,143,165,187,209\displaystyle 121, 143, 165, 187, 209. The term 186\displaystyle 186 violates this pattern and is the wrong term.

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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