Lesson 2.2: Coding-Decoding

Introduction:
Coding-Decoding questions are common in SSC exams. These test your logical thinking by identifying patterns in words, letters, or numbers and translating them into codes.

1. Letter Coding

• Definition: Letters of a word are replaced by other letters according to a pattern.

• Types:

  1. Shift Coding: Each letter shifted forward/backward in alphabet.

     • Example: A → D, B → E, C → F (Shift +3)

  2. Reverse Coding: Alphabet reversed (A→Z, B→Y…)

  3. Substitution Coding: Each letter replaced with a fixed letter.

2. Number Coding

• Letters of a word assigned numbers.

• Example:
  CODE → C=3, O=15, D=4, E=5
  Sum of letters = 3+15+4+5 = 27

3. Mixed Coding

• Combines letters and numbers or uses patterns like alternating shifts.

• Example:
  CAT → DZU (Shift +1 for first letter, -1 for second, +2 for third)

4. SSC Exam Tips

• Read instructions carefully for pattern.

• Check for consistent shifts or substitutions.

• Practice both letter and number coding questions.

• Solve quickly using shortcut methods.

5. Practice Questions

1. If TABLE → UBCMF, then CHAIR → ?

2. In a code, A=3, B=5, C=7. Word CAB = ?

3. If FLOWER → GNPXFS, then RIVER → ?

4. In a certain code, letters are reversed. BOOK → ?

5. If DOG → 4 15 7, then CAT → ?