Mathematics: Tips for Solving Coding and Decoding Problems in Competitive Exams

Tips for Solving Coding and Decoding Problems

Coding-decoding is the simplest from of verbal intelligence reasoning. In this type of questions, a set of letters or numbers are given in code which have to be deciphered or decoded. In other words, here letters or alphabet do not stand for themselves but for some other letter ie, they have an artificial or code value. These artificial or code values are given according to some set principle or pattern. By applying the same principle, one can decode the coded identify.

     Although, the majority of questions of this type are based on English alphabet, but still it can be divided into two types.

1. Letter Coding: In this category, certain letters of alphabet stand for certain other letters of alphabet.

Ex:- HOUSE → IPVTF

In this case, each letter is replaced by its following letter in the alphabet, ie, H by I, O by P and so on.

2. Number Coding: In this category, letters are changed by the number of letters in their corresponding alphabetic position. There are several methods of number coding.

( i ) Position number of letters remain the same.

•      Ex:- LIGHT → 1297820

( ii ) Position number of letters are added.

•   Ex:- MAN → 28

( iii ) Position numbers of letters are added but at the same time a certain number is subtracted, added, multiplied or divided.

• Ex:- MAN → 7

Here, (13+1+14) ÷ 4 = 28 ÷ 4 = 7

Memorization of following facts could be useful to answer this type of questions.

( a ) Position number of letters in the alphabet.

A   B   C   D   E     F   G   H   I    J    K    L   M   

1   2    3    4    5    6   7   8    9   10  11  12  13

N      O    P    Q    R    S    T     U    V     W    X    Y    Z

14   15   16   17  18   19   20   21  22   23   24   25   26

( b ) Position numbers of each letters in the alphabet in reverse order.

A     B     C    D     E     F   G     H    I     J    K    L    M   

26   25   24   23   22   21  20   19  18   17  16   15  14

N      O    P    Q    R    S    T     U    V     W     X    Y    Z

13   12   11   10    9   8     7     6      5      4    3    2    1

( c ) Opposite letters of each letter in the alphabet.

A ↔ Z, B ↔ Y, C ↔ X, D ↔ W, E ↔ V, F ↔ U, G ↔ T, H ↔ S, I ↔ R, J ↔ Q, K ↔ P, L ↔ O, M ↔ N, N ↔ M.

Sample Problems 

1) In a certain code language "NAME" is written as "OBNF". How will "SHIP" be written in that code ?

Solution:

NAME → OBNF

 Here N + 1 = O, A + 1 = B, M + 1 = N, e + 1 = F

In the same way, S + 1= T, H + 1 = I, I + 1 = J, P + 1 = Q

There fore Answer is TIJQ

2) In a certain code language "LOSE" is written as "MQVI. How will "GAIN" be written in that code ?

Solution: 

LOSE → MQVI

Here L + 1 = M, O + 2 = Q, S + 3 = V, E + 4 = I

In the same way, G + 1 = H, A + 2 = C, I + 3 = L, N + 4 = R

There fore Answer is HCLR