Coding-Decoding for Sainik School Class 6th & 9th

Coding-Decoding for Sainik School Class 6th & 9th

Coding-Decoding is a common reasoning topic often asked in competitive exams and entrance tests like the Sainik School entrance exam. It involves patterns and logic, where letters or numbers are substituted or coded to represent something else. The idea is to find the pattern and decode or encode the given information.

Basic Concepts:

1. Letter Substitution:
   • In this type of coding, each letter is replaced with another letter according to a specific rule or pattern.
   • Example: If the pattern is that each letter is replaced with the next one in the alphabet, then A becomes B, B becomes C, and so on.
     • Code for “CAT” could be “DBU” (each letter is shifted by one).
2. Number Substitution:
   • In some questions, numbers are used to replace letters or groups of letters.
   • Example: If A = 1, B = 2, C = 3, then the word “BAT” will be coded as 2 1 20.
3. Reverse Order Coding:
   • The letters may be coded in reverse order from the alphabet.
   • Example: If A = Z, B = Y, etc., the word “HELLO” would be coded as “SVOOL”.
4. Pattern or Shift Coding (Caesar Cipher):
   • One of the most common coding methods is the Caesar Cipher, where each letter is shifted by a certain number.
   • Example: If the shift is 3, A becomes D, B becomes E, and so on.
     • Word “DOG” will become “GRJ” if the shift is 3.
5. Substitution with a Key Word or Phrase:
   • Sometimes, a key phrase or word is used to substitute letters. Each letter of the alphabet is substituted with a corresponding letter from the key.
   • Example: A keyword like “SCHOOL” may be used to substitute letters based on its position.
6. Alphanumeric Code:
   • Numbers and letters are often mixed to create a code.
   • Example: “5” could replace E and “1” could replace I in certain cases, creating an alphanumeric pattern.
7. Mirror Image Coding:
   • The position of the letters can also be reversed in this type of coding.
   • Example: The word “APPLE” may be coded as “ELPPA”.

Examples:

1. Example 1 – Letter Shift:
   • Q. If A = 1, B = 2, C = 3, and so on, what is the code for the word “SCHOOL”?
     • A. S = 19, C = 3, H = 8, O = 15, O = 15, L = 12
     • Answer: 19 3 8 15 15 12
2. Example 2 – Letter Substitution:
   • Q. If A = Z, B = Y, C = X, and so on, what is the code for “LOVE”?
     • A. L = O, O = L, V = E, E = V
     • Answer: OLLV
3. Example 3 – Reverse Word Coding:
   • Q. If “GREAT” is coded as “TEARG”, what is the code for “LEARN”?
     • A. “NRAEL”

Key Points for Preparation:

• Identify the Pattern: Carefully study the given code and try to identify the logic behind it (letter shifting, substitution, mirror image, etc.).
• Practice with Examples: Regular practice of various coding-decoding questions helps in understanding different types of patterns.
• Understand Different Coding Types: Learn how letters, numbers, and their positions can be manipulated to form codes.
• Speed and Accuracy: Work on solving coding-decoding problems quickly and accurately to gain confidence.

By understanding these techniques and practicing consistently, students can become proficient in solving coding-decoding questions for the Sainik School entrance exams for both Class 6th and Class 9th.