Number Series, Coding and DecodingPYQ Jan 26Question 4520 of 217

Find the odd number in the following series: 7, 11, 13, 15, 19, 23, ...

A11

B13

C15

D19

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Correct Answer

✅ Option c — 15

Let us examine the numbers in the given series:

\displaystyle 7, 11, 13, 15, 19, 23, \dots

\displaystyle 7

is a prime number (has only

\displaystyle 1

and itself as factors).
-

\displaystyle 11

is a prime number.
-

\displaystyle 13

is a prime number.
-

\displaystyle 15

is a composite number (factors are

\displaystyle 1, 3, 5, 15

).
-

\displaystyle 19

is a prime number.
-

\displaystyle 23

is a prime number.

Since all other numbers in the series are prime numbers except

\displaystyle 15

, the number

\displaystyle 15

is the odd one.

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

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.

Exam Strategy Tip

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

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