Coding and Decoding

Coding and Decoding is an important part of Logical reasoning section in all aptitude 

related examinations. 

Coding is a process used to encrypt a word, a number in a particular code or pattern 

based on some set of rules. 

Decoding is a process to decrypt the pattern into its original form from the given codes. 

Letter Coding In this type of questions, alphabets of a word are replaced by some other 

alphabets according to specific rule to form code. 

Number Coding In this type of questions, a word is replaced by certain numbers 

according to some specific rule. 

 

Sample Problems – 

 

 

 

 

Question 1: If EARTH is written as FCUXM in a certain code. How is MOON written in 

that code? 

Solution : 

 

Question 2: If DELHI is written as EDMGJ in a certain code. How is NEPAL written in 

that code? 

Solution : 

 

   

 

 

 

 

 

 

Question 3: If SYMBOL is written as NZTMPC is a certain code. How is NUMBER written 

in that code? 

Solution : Acc. to question 

 

Question 4: In a certain code, COMPUTER is written as PMOCRETU, how is DECIPHER 

written in that code? 

Solution : Acc. to question 

 

 

 

 

Question 5: In a certain code, NEWYORK is written as 111, how is NEWJERSEY written 

in that code? 

Solution : In NEWYORK 

N = 14, E = 5, W = 23, Y = 25, O = 15, R = 18, K = 11 

Total = 14 + 5 + 23 + 25 + 15 + 18 + 11 = 111 

In NEWJERSEY 

Total = 14 + 5 + 23 + 10 + 5 + 18 + 19 + 5 + 25 

= 124 

Question 6: In a certain code, HARYANA is written as 8197151, how is DELHI written in 

that code? 

Solution : We used the number of alphabets here. 

H = 8 

A = 1 

R = 18 = 1+8 = 9 

Y = 25 = 2+5 = 7 

For DELHI 

D = 4 

E = 5 

L = 12 = 1+2 = 3 

H = 8 I = 9 Hence, DELHI is written as 45389. 

Question 7: In a certain code BOMB is written as 5745 and BAY is written as 529, how is 

BOMBAY written in that code? 

Solution : Acc. to question 

Use the numbers to relate the words 

B O M B B A Y -> B O M B A Y

5 7 4 5 5 2 9 5 7 4 5 2 9

1. Letter coding:

In this, we are going to deal with the types of questions, in which the letter of a word are replaced by certain other letters according to a specific pattern/rule to form a code. 

Candidates are required to decipher the pattern of coding to substitute the given word from the given alternative. 

 

 

 

 

 

 

 

 

Example.1. In a certain code language ‘BOXER’ is written as ‘AQWGQ’. What will be the code of ‘VISIT’ in that code language? 

(A) UKRKS (B) WKRKS (C) UKRKU (D) WKRKU Ans. A 

Solution: 

 

Important Note: -   

* The pattern of codded language i.e., simple, reverse, cross and replacement. 

* Try to solve these questions with the help of alphabetical values. 

* The pattern of coding may easily be brought out in mind with the help of alphabetical values. 

2. Number Coding: 

In this, we are going to deal with the questions, in which the numerical code values are assigned to a word or alphabets according to predefined pattern. 

Candidates are required to identify the numerical pattern of coding so that the given word can be transform in same coding. 

Example.1. If ‘ACNE’ is coded as 3 7 29 11, then what will be code for ‘BOIL’ in that code language? 

(A) 5 29 19 27 

(B) 5 31 19 25 

(C) 5 29 19 25 

(D) 5 31 21 25 

Ans. B 

Solution 

 

3. Substitution Coding: 

In such question, we are going to deal with the pattern of coding in which codes are assigned by the substitution method where in an artificial alternative is assigned to a given word and candidates are required to decipher the coding pattern to substance the other given word. 

Example.1. If yellow is called blue, blue is called red, red is called pink, pink is called black and black is called orange, then what is the colour of blood? 

(A) Yellow 

(B) Pink 

(C) Blue 

(D) Orange 

Ans. B 

Solution  

We know, colour of blood = red 

But according to question, 

red = pink 

Therefor, the colour of blood = pink 

 

 

 

Important Note:  

For such type of questions, two types of methods are there, 

→ called → ‘white’ is called ‘grey’. 

Here, ‘grey’ is the code of ‘white’. 

→ means → ‘white’ means ‘grey’. 

Here, ‘white’ is the code of ‘grey’. 

4. Deciphering Coding:  

In these types of question, we are going to deal with a message bearing a common code for given word/numeral. Candidates are required to identify the code from the common property of word/numeral and decipher the given codes with best alternatives. 

Example.1. In a certain code language,  

‘more money in market’ is written as ‘zo li aa to’, 

‘share in market profit’ is written as ‘vo to je li’, 

‘making more profit now’ is written as ‘su je zo ka.’ And 

‘now the market gains’ is written as’ do li yo su.’ 

Which of the following does ‘vo’ stand for? 

(A) profit 

(B) in 

(C) market 

(D) share 

Ans. B 

 

Important Notes: 

* While dealing such questions, choose the common term from the given statement. 

* More than one statement is to be used for selecting the common term. 

5. Symbol Coding:  

In this, we are going to deal with the questions, in which a set of symbol is assigned to a group of letter. Candidates are required to identify the relation between the letter and symbol and decipher the pattern of coding and choose the best alternative as well. 

 

 

 

 

 

Ex.1. In a certain code ‘TRAIN’ is written as ‘39*7%’ and ‘MEAL’ is written as ‘4$*@’. How is ‘ITEM’ written in that code? 

(A) 7$34 

(B) 73$4 

(C) 79$4 

(D) 73*4 

Solution  

Ans. B. 

 

Solved Example with Solution: Q.1. If SMART is coded as UKCPV, then WONDER is coded as 

(A) YMPPRT 

(B) YMPBGP 

(C) YMPBFP 

(D) YMBPPG 

Answer  

Ans . B 

Solution  

 

 

 

 

Q.2. If DELHI is codded as 73541 and CALCUTTA as 82589662, then how can CALICUT be coded? 

(A) 5279431 

(B) 5978013 

(C) 8251896 

(D) 8543691 

Answer  

Ans . C 

Solution  

 

 

 

 

 

 

Q.3.If in a code language, ‘white’ means ‘black’, ‘black’ means ‘yellow’, ‘yellow’ means ‘blue’, ‘blue’ means ‘red’ and ‘red’ means ‘green’, then what is the colour of human blood? 

(A) Yellow 

(B) Blue 

(C) Red 

(D) Green 

Answer  

Ans . B 

Solution  

As, we know that the colour of human blood is red, here blue means red. Hence, colour of human blood is ‘blue’ 

 

 

 

 

 

 

 

Q.4. In a certain language ‘oka peru’ means ‘fine cloths’, ‘meta lisa’ means ‘clear weather’, which word of that language means ‘weather’? 

(A) peru 

(B) oka 

(C) meta 

(D) dona 

Answer  

Ans . D 

Solution  

Oka → fine cloth ------(i) 

meta lisa → clear water--------(ii) 

dona lisa peru → fine clear weather. 

From Eqs. (i) and (iii), 

peru → fine 

from Eqs. (ii) and (iii), 

lisa → clear 

Hence, 

dona → weather 

  

Q.5. In a certain code, ‘DOWN’ is written as ‘5@9#’ and ‘NAME’ is written as ‘#6%3’. How would ‘MODE’ be written in that code? 

(A) %653 

(B) %@63 

(C) %5@3 

(D) %@53 

Answer  

Ans . D 

Solution  

  

 

 

Coding Decoding Questions for Practice:

Q.1.If in a certain code, LUTE is written as MUTE and FATE is written as GATE, then how will BLUE be written in that code? 

(A) CLUE 

(B) GLUE 

(C) FLUE 

(D) SLUE 

Answer  

Ans . A 

 

Q.2. In a certain code, ROAD is written as URDG. How is SWAN written in that code? 

(A) VXDQ 

(B) VZDQ 

(C) VZCP 

(D) UXDQ 

Answer  

Ans . B 

 

 

Q.3.In a certain code language, OPERATION is written as NODQBUJPO. How is INVISIBLE written in that code? 

(A) JOWJTJCMF 

(B) JOWJTHAKD 

(C) HMUHTJCMF 

(D) HMUHTHAKD 

Answer  

Ans . C 

 

Q.4. In a certain code, FAVOUR is written as EBUPTS. How is DANGER written in that code? 

(A) CBFFDS 

(B) CBMHDS 

(C) EBFHDS 

(D) EBHHFS 

Answer  

Ans . B 

 

 

Q.5.If SUMMER is coded as RUNNER, the code for WINTER will be 

(A) SUITER 

(B) VIOUER 

(C) WALKER 

(D) SUFFER 

Answer  

Ans . B 

 

Q.6. In a certain code, PRODUCTIONS is written as QQPCVEUHPMT. How is ORIENTAITON written in that code? 

(A) PQJDOVBSJNO 

(B) PQJDOUBUJPO 

(C) PSJFOVBSNO 

(D) NSHFEMVBSJNO 

Answer  

Ans . A 

 

 

 

Q.7. If TRUTH is coded as SUQSTVSUGI, then the code for FALSE will be 

(A) EGZBKMRDE 

(B) EGZKMRTDF 

(C) EGZBKMRTDF 

(D) FGZBKNRTDF 

Answer  

Ans . C 

 

Q.8. In a certain code language ORIENTAL is written as MBUOFJSP. How is COWARDLY written in that code language ? 

(A) XKCQBXPD 

(B) XLBQCXPD 

(C) ZMESBXPD 

(D) ZMDSEPXB 

Answer  

Ans . C 

 

 

Q.9. In a certain code language, COMPUTER is written as RFUVQNPC. How is MEDICINE written in the same code? 

(A) EOJDEJFM 

(B) EOJDJEFM 

(C) MFEDJJOE 

(D) MFEJDJOE 

Answer  

Ans . B 

 

Q.10. In a certain code, MONKEY is written as XDJMNL. How is TIGER written in that code? 

(A) QDFHS 

(B) SDFHS 

(C) SHFDQ 

(D) UJHFS 

Answer  

Ans . A