Number Series, Coding and DecodingMCQPYQ Nov 20Question 2014 of 217
All Questions

Find the missing value in the series 0,2,3,6,10,17,28,?,75\displaystyle 0, 2, 3, 6, 10, 17, 28, ?, 75.

Options

A58
B46
C48
D54
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Correct Answer

Option b46

All Options:

  • A58
  • B46
  • C48
  • D54

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Detailed Solution & Explanation

We are given the series: 0,2,3,6,10,17,28,?,75\displaystyle 0, 2, 3, 6, 10, 17, 28, ?, 75
Let's analyze the relation between consecutive terms. We notice a tri-nacci type recurrence relation where each term is the sum of the preceding two terms plus 1\displaystyle 1:
an=an1+an2+1for n3a_n = a_{n-1} + a_{n-2} + 1 \quad \text{for } n \ge 3
Let's verify this pattern:
- a3=a2+a1+1    2+0+1=3\displaystyle a_3 = a_2 + a_1 + 1 \implies 2 + 0 + 1 = 3
- a4=a3+a2+1    3+2+1=6\displaystyle a_4 = a_3 + a_2 + 1 \implies 3 + 2 + 1 = 6
- a5=a4+a3+1    6+3+1=10\displaystyle a_5 = a_4 + a_3 + 1 \implies 6 + 3 + 1 = 10
- a6=a5+a4+1    10+6+1=17\displaystyle a_6 = a_5 + a_4 + 1 \implies 10 + 6 + 1 = 17
- a7=a6+a5+1    17+10+1=28\displaystyle a_7 = a_6 + a_5 + 1 \implies 17 + 10 + 1 = 28
Following this established recurrence relation, the missing term a8\displaystyle a_8 is:
a8=a7+a6+1=28+17+1=46a_8 = a_7 + a_6 + 1 = 28 + 17 + 1 = 46
Let's verify the final term using a8=46\displaystyle a_8 = 46:
a9=a8+a7+1=46+28+1=75a_9 = a_8 + a_7 + 1 = 46 + 28 + 1 = 75
This matches the final term perfectly.
Hence, **Option B** 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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