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Vidaara.orgClass 8 · Mathematics
CodeVID-M08-23-COD-01
Coding-Decoding Basics - Assignment
Chapter: Logical Reasoning
Topic: Coding-Decoding Basics
Maximum Marks: 35
Time: 75 minutes
Name: ____________________ Roll No.: __________ Date: ____________

General Instructions

  • All questions are compulsory.
  • Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
  • Show all working for Sections B, C and D. Only final answers are given at the end — for full solutions, raise your doubts with your teacher.
Section A — Multiple Choice Questions 5 × 1 = 5 marks
1.
In coding-decoding, symbols follow a:
  • A.colour
  • B.rule
  • C.shape
  • D.size
2.
If each letter moves $+1$, CAT becomes:
  • A.DBU
  • B.BZS
  • C.CAT
  • D.ECV
3.
To decode, you ___ the coding rule.
  • A.repeat
  • B.reverse
  • C.ignore
  • D.double
4.
With $A=1, B=2, \ldots$, the letter $E$ is:
  • A.$4$
  • B.$5$
  • C.$6$
  • D.$3$
5.
With $A=1,\ldots,Z=26$, this is a ___ code.
  • A.colour
  • B.number
  • C.shape
  • D.sound
Section B — Short Answer (2 marks) 4 × 2 = 8 marks
6.
With $A=1, B=2, \ldots$, find the code for $D$.
7.
If each letter moves $+1$, code the word "AB".
8.
If "CAT" is "DBU" ($+1$), decode "DBU".
9.
What is the position of the letter $E$ in the alphabet?
Section C — Short Answer (3 marks) 4 × 3 = 12 marks
10.
If each letter shifts $+2$, code "BAD".
11.
If "DOG" is coded "EPH" ($+1$), code "CAT".
12.
Using $A=1,\ldots,Z=26$, find the number code for "BED".
13.
If "123" stands for "ABC", decode "312".
Section D — Long Answer (5 marks) 2 × 5 = 10 marks
14.
In a code each letter is shifted forward by $3$ (A$\to$D, B$\to$E, $\ldots$). Code "MATH" and decode "FRGH".
15.
Using $A=1, B=2, \ldots, Z=26$, write the number code for "MATHS" and find the sum of those numbers.

Answer Key

Section A — Multiple Choice Questions
  1. (B) rule
  2. (A) DBU
  3. (B) reverse
  4. (B) $5$
  5. (B) number
Section B — Short Answer (2 marks)
  1. $4$.
  2. "BC".
  3. "CAT".
  4. $5$.
Section C — Short Answer (3 marks)
  1. "DCF".
  2. "DBU".
  3. $2, 5, 4$.
  4. "CAB".
Section D — Long Answer (5 marks)
  1. MATH $=$ PDWK; FRGH $=$ CODE.
  2. $13, 1, 20, 8, 19$; sum $61$.
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