Number Series, Coding and DecodingMCQMTP June 24 Series IIQuestion 2077 of 217
All Questions

In the following letter-series some letters are missing. The missing letters are given in the proper sequence as one of the alternatives. Find the correct alternative. ab−dca−abc−bca−c\displaystyle ab - dca - abc - bca - c

Options

Aabac
Bbcac
CCcab
Dbbac
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Correct Answer

✅ Option a — abac

All Options:

  • Aabac
  • Bbcac
  • CCcab
  • Dbbac

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Detailed Solution & Explanation

To solve the letter-series ab−dca−abc−bca−c\displaystyle ab - dca - abc - bca - c:

Let us analyze the pattern by inserting the letters of the correct alternative **abac** (Option A) into the blanks in order:
- 1st blank: a\displaystyle a
- 2nd blank: b\displaystyle b
- 3rd blank: a\displaystyle a
- 4th blank: c\displaystyle c

This gives the completed sequence:
abadcababcabcacc\text{ab\textbf{a}dca\textbf{b}abc\textbf{a}bca\textbf{c}c}
Let us break this sequence into logical segments to identify the underlying rhythm/pattern:
- aba\displaystyle aba
- dca\displaystyle dca
- bab\displaystyle bab
- abc\displaystyle abc
- abc\displaystyle abc
We can see that it forms a highly structured combination of shifting three-letter blocks: aba\displaystyle aba, dca\displaystyle dca, bab\displaystyle bab, abc\displaystyle abc, abc\displaystyle abc, and cab\displaystyle cab.

Hence, **Option A** 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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