Number Series, Coding and DecodingMCQPYQ July 21Question 2021 of 217

The wrong term in the series $\displaystyle 225, 196, 169, 144, 121, 100, 77, 64$ , is:

A121

B77

C100

D169

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Correct Answer

✅ Option b — 77

We are given the series:

\displaystyle 225, 196, 169, 144, 121, 100, 77, 64

Let's express each term as a perfect square:
-

\displaystyle 225 = 15^2

\displaystyle 196 = 14^2

\displaystyle 169 = 13^2

\displaystyle 144 = 12^2

\displaystyle 121 = 11^2

\displaystyle 100 = 10^2

\displaystyle 77

(not a perfect square)
-

\displaystyle 64 = 8^2

The sequence consists of squares of descending consecutive natural numbers:

\displaystyle 15^2, 14^2, 13^2, 12^2, 11^2, 10^2, 9^2, 8^2

.
The seventh term should be

\displaystyle 9^2 = 81

instead of

\displaystyle 77

.
Therefore,

\displaystyle 77

is the wrong/incorrect term in the series.
Hence, **Option B** 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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