# 9th Class Mental Ability Coding-Decoding

Coding-Decoding

Category : 9th Class

CODING-DECODING

Learning Objectives

• Introduction
• How to Decode
• Types of Problems

Introduction

In Coding and Decoding test means “Secret messages” are given in code and they have to be decoded. Another words, “we can say that this is a method of transmitting a message between the sender and the receiver, which third person cannot understand easily”. This test is given to judge the students, candidate’s ability to decipher the rule which is applied for coding a particular message and break code to reveal the message.

How to Decode

In reasoning, words, letters and numbers are coded according to a certain rule. While solving problems, student has to identify that particular rule 1st and then the same rule is applied to decode other coded words, letters, number etc. The types of coding decoding problems will give you more clear concept about it. But before coming to the actual problems, we must remember the positions of letters in English alphabet in forward order that will help you in solving problems of coding-decoding.

Let us see the positions:

Table 1:

Positions of letters in forward order (Left to Right)

 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

Table 2:

Positions of letters in forward order (Left to Right)

 Z Y X W V U T S R Q P O N 1 2 3 4 5 6 7 8 9 10 11 12 13 M L K J I H G F E D C B A 14 15 16 17 18 19 20 21 22 23 24 25 26

Table 3:

Opposite letters

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

Types of Problems

Coding - Decoding in Forward Sequence

In such problems, letters are coded in forward alphabetical sequence,

Example 1

• If ‘EDEFF’ is coded as ‘GGHIH’, then ‘NLMNF’ will definitely be coded as ‘POPQV’.

Explanation:

Here, three middle letters ‘DEF’ shift three places in forward alphabetical sequence while 2 extreme elements E and F shifts 2 places in forward alphabetical sequence.

Let us see:

Similarly, 3 middle letters of ‘NLMNT’ shift three places in forward alphabetical order while extreme letters shift 2 places forward.

Let us see:

Clearly, code for ‘NLMNT’ is ‘POPQV’.

Example 2

• If ‘KGOTT’ is coded as ‘NIQVW’, then ‘TTOPP’ will definitely be coded as ‘WVQRS’.

Explanation:

Here, two letters shift two places in forward alphabetical sequence while extreme letters shift three places in forward alphabetical order.

Let us see:

Similarly, three middle letters will move two places forward but two extreme letters T and P will move 3 places forward.

Let us see:

Note: In forward sequence coding-decoding ‘Table - 1’is used.

Commonly Asked Questions

• If code of ‘RLMNA’ = ‘VOPQE’, then find the code for ‘FPQRL’.

(a) JSTUP                      (b) PUTSJ

(c) STJUP                      (d) STJPU

(e) None of these

Answer: (a)

Explanation: Option (a) is correct. Because in this case three middle letters are coded three places forward but extreme letters R and A are coded 4 places forward

Let us see:

Code for ?RLMNA?:

Similarly,

Code for ?FPQRL?:

Clearly, code for ‘FPQRL’ is ‘JSTUP’. Rest of the options is incorrect because of the correctness of option (A).

• If ‘DWOS’ is coded as ‘EYQT’, then ‘GNEM’ will be coded as

(a) NGPH                      (b) HPGN

(c) NGHP                      (d) NHGP

(e) None of these

Answer: (b)

Explanation: Option (b) is correct. Because in this case two middle letters are coded two places forward while extreme letters are coded one letter forward.

Let us see:

Code for ?DWOS?:

Similarly,

Code for ?GNEM?:

Clearly, code for ‘GNEM’ is ‘HPGN’. Rest of the options is incorrect because of the correctness of option (B).

Coding - Decoding in Backward Sequence

In such problems, letters are coded in backward alphabetical sequence.

Example 1

• If ‘LLMTT’ is coded as ‘GKLSO’, then ‘TDEPR’ will definitely be coded as ‘KCDOIVT’.

Explanation:

Here, three middle letters ‘LMT’ are coded one place backward while extreme letters L and T are coded 5 letters backward.

Let us see:

Similarly, three middle letters of ?PDEPR? are coded one place backward.

Let us see:

Clearly, code for ‘PDEPR’ is ‘KCDOM’.

Example 2

• If ‘PROSET’ is coded as ‘NPMQCR’, then ‘KNOSEZ’ will definitely be coded as ‘LMQCX’.

Explanation:

Here, letters of ‘PROSET’ are coded two places backward.

Let us see:

In the same manner, letters of ?KNOSEZ? are coded two place backward.

Let us see:

Clearly, code for ‘KNOSEZ’ is ‘ILMQCX’.

Note: In backward sequence coding-decoding ‘Table - 1’ is used.

Commonly Asked Questions

• If code for ‘PSODI’ is ‘NQMBG’, then what will be the code for ‘GGHPP’?

(a) NFEFN                     (b) FEENN

(c) NEFFN                      (d) EEFNN

(e) None of these

Answer: (d)

Explanation: Option (d) is correct because in this case letters are coded two letters backward.

Let us see:

Code for ?PSODI?:

Similarly,

Code for ?GGHHP?:

Clearly, code for ‘GGHPP’ is ‘EEFNN’.

Rest of the options is incorrect because of the correctness of option (D).

• If ‘HZDIECT is as ‘BYCHDK’ then ‘XNETL’ will be coded as

(a) RMDSKS                  (b) RSDMSS

(c) RDMSKS                   (d) RSDMKS

(e) None of these

Explanation: Option (a) is correct because in this case four middle letters are coded one place backward while extreme letters are coded 6 places backward.

Let us see:

Code for ?HZDIEQ?:

Similarly,

Code for ?XNETL?:

Clearly, code for ‘XNETLY’ is ‘RMDSKS’.

Rest of the options is incorrect because of the correctness of option (A).

Coding - Decoding in Forward - Backward Sequence

In such pattern, letters are coded backward and forward or der forward and backward order alternately.

• If ‘PQMDS’ is coded as ‘WOBLT’, then ‘CDBXP’ will definitely be coded as ‘TBDVR’.

Explanation:

Here, in ‘PQMDS’ P is coded 2 places forward, Q is coded 2 places backward and M is coded 2 places forward D is coded 2 places backward and S is coded 2 places forward.

Let us see:

Similarly, in ‘CDBXP’, C is coded two places forward D is coded two places backward B is coded 2 places forward X is coded 2 places backward and P is coded 2 letters forward.

Let us see:

Example 2

• If ‘FPLL’ is coded as ‘AUGQ’, then ‘HJNIST’ will definitely be coded as ‘COIS’.

Explanation:

Here, letters are coded 5 places backward and 5 places forward alternately.

Let us see:

Similarly,

Code for ?HJNN?:

Clearly, code for ‘HJNN’ is ‘COIS’.

Note: In forward- backward sequence coding-decoding ‘Table -1’ is used.

Commonly Asked Questions

• If ‘LEFNES’ is coded as ‘NCHLGQ’, then ‘DLTIMEQ’ will be coded as............

(a) FJVLOG                   (b) FJLVGO

(c) FJVLGO                   (d) FVJLGO

(e) None of these

Answer: (c)

Explanation: Option (c) is correct because letters are coded two places forward and backward alternately.

Let us see:

Code for ?LEFNES?:

Similarly,

Code for ?DLTNEQ?:

Clearly, code for ‘DLTNEQ’ is ‘FJVLGCY’.

Rest of the options is incorrect because of the correctness of option (C).

• If ‘PLDQ’ is coded as ‘UGIL’, then how will ‘SNPG’ be coded?

(a) XIUB                        (b) XUBI

(c) XUIB                        (d) XBUI

(e) None of these

Answer (a)

Explanation: Option (a) is correct because letters are coded 5 places forward and 5 places backward alternately.

Let us see:

Code for ?PLDQ?:

Similarly,

Code for ?SNPG?

Clearly, code for ‘SNPG’ is ‘XIUB’.

Rest of the options is incorrect because of the correctness of option (A).

Coding-Decoding by Reversing Letters

In such problems the 1st letter from right takes the 1st place from left the 2nd letter from right takes the 2nd position from left the 3rd letter from right takes the 3rd place from left and the process goes on till all the letters get arranged in this manner.

Example 1

If ‘LMNOPQ’ is coded as ‘QPONML’, then ‘STUVWX’ Will Definitely be coded as ‘XWVUTS’

Explanation:

‘LMNOPQ’ is coded in reverse order as ‘QPONIVIL’

Similarly, ‘STUVWX’ will be coded by writing the letters In reverse order Therefore, The code for ‘STUVWX’ will be

‘NAMESA’ Kr is coded as then will definitely be as

Explanation:

‘NAMESAKE’ is coded in reverse order as ‘EKASEMAS’. In the same way the code for ‘INCREASE’ has been obtained by writing it in reverse order as ‘ESAERCN’

Commonly Asked Questions

• Code for ‘BLACK’ = ‘KCALB’, then code for ‘TEMPERATURE’ =‘?’

(a) ERUATREPMET        (b) ERUTAREPMET

(c) ERUTARPEMET        (d) EURTAREPMET

(e) None of these

Explanation: Option (b) is correct because coding has been done by writing the letters of words in reverse order.

Rest of the options is incorrect because of the correctness of option (B).

If ‘BRING’ is coded as ‘GNIRB’ then ‘ACCURATE’ will be coded as

(a) ETRACUCA              (b) EATRUCCA

(c) EATRCCUA              (d) ETARUCCA

(e) None of these

Explanation: Option (d) is correct because here, the letters of given word ‘BRING’ has been coded by writing them in reverse order. Following the same pattern the code for ‘ACCURATE’ will be ‘ETARUCCA’.

Rest of the options is incorrect because of the correctness of option (D).

Coding-Decoding Based on Numbers and Letters

In such problems, numerical code values are given to words and letter code values are given to numbers.

Example 1

If in a certain code language, ‘A’ is coded as ‘4’,‘B’ is coded as ‘5’ ‘X’ is coded as ‘6’ and so on then code for ‘BCCFABF’ will definitely be ‘5669459’.

Explanation:

In this case, letters are coded as below:

 A B C D E F ? ? ? 4 5 6 7 8 9 ? ? ?

Now,

 B C C F A B F 5 6 6 9 4 5 9

Clearly, the code for ‘BCCFABF’ is ‘5669459’

Example 2

In a certain code,‘3’ is coded as ‘S’; ‘4’ is coded as ‘T’; ‘5’ is coded as ‘B’; ‘6’ is coded as ‘H’ and 7 is coded as ‘M’ then the code for ‘57743645’ will definitely be ‘BMMTSHTB’.

Explanation:

Here, alphabetical code values are given for numbers. Therefore, the code for numbers will be as follows:

 3 4 5 6 7 P Y X W V

Now,

 5 7 7 4 3 6 4 5 B M M T S H T B

Clearly, the code for ?57743645? is ?BMMTSHTB?.

Commonly Asked Question

• Just see the following letter codes and find the code for ‘RZZLGPSS’.

 G L P Q R S T U Z 3 1 9 4 7 2 6 5 8

(a) 78813922                 (b) 78

(c) 78183922                  (d) 126874

(e) None of these

Answer: (a)

Explanation: Option (a) is correct.

Let us see:

 R Z Z L G P S S 7 8 8 1 3 9 2 2

Clearly, code for ‘RZZLGPSS’ is ‘78813922’

Rest of the options is incorrect because of the correctness of option (A),

• In a certain code language ‘5’ is coded as ‘P’; ‘7’ is coded as ‘R’; ‘8’ is coded as ‘X’: ‘9’ is coded as ‘Y’ Then how will ‘YRPPXPYYR’ be coded?

(a) 975558997               (b) 955785997

(c) 975599857                (d) 975585997

(e) None of these

Answer: (d)

Explanation: Option (d) is correct.

Let us see:

 Y R P P X P Y Y R 9 7 5 5 8 5 9 9 7

Clearly, code for ‘YRPPXPYYR’ is ‘975585997’.

Rest of the options is incorrect because of the correctness of option (D).

Opposite Letters Coding - Decoding

Such problems are based on opposite letters (See Table 3).

Example 1

If ‘HDC is coded as ‘SWX’, then ‘TSR’ will definitely be coded as ‘GHI’.

Explanation:

• ‘H’ is opposite letter of ‘S’; ‘D’ is opposite letter of ‘W’ and ‘C’ is opposite letter of ‘X’.

Similarly, ‘V’ is opposite letter of ‘G’; ‘S’ is opposite letter of ‘H’ and ‘R’ is opposite letter of ‘H’ and ‘R’ is opposite letter of ‘I’. Hence, based on this logic ‘GHI’ will be the code for ‘TSR’.

Example 2

• If code for ‘V’ is ‘E’, then ‘P’ will definitely be coded as ‘K’.

Explanation:

‘V’ is opposite letter of ‘E’. Similarly of ‘p’ is opposite letter of ‘K’

Note: To solve problems always keep in mind ‘Table-3’

Commonly Asked Questions

• If ‘XUT’ is coded as ‘CFG’, then how will ‘DKM’ be coded?

(a) WPN                        (b) NPW

(c) PWN                        (d) NWP

(e) None of these

Answer: (a)

Explanation: Option (a) is correct because ‘X’ and ‘C’, ‘U’ and ‘F’ and ‘T’ and ‘G’ are opposite letters. Similarly, ‘DKIVT’ will be coded by its opposite letters ‘WPN’.

Rest of the options is incorrect because of the correctness of option (A).

• If the code for ‘VRO’ = ‘EIL’, then code for ‘NZS’ =‘?’

(a) AHM                        (b) HAM

(c) MHA                       (d) MAH

(e) None of these

Answer: (d)

Explanation: Option (d) is correct because

Opposite letter of ‘V’ = ‘E’

Opposite letter of ‘R’ = ‘I'

Opposite letter of ‘O’ = ‘L’

Similarly,         Opposite letter of ‘W’ = ‘IVT’

Opposite letter of ‘T’ = ‘W’

Opposite letter of ‘S’ = ‘W’

Clearly, code for ‘NZS’ = ‘MAH’.

Rest of the options is incorrect because of the correctness of option (D).

Coding - Decoding Based on Letter Positions in Alphabet

In such problems, letters are coded on the basis of forward/backward alphabet sequence.

Example 1

If ‘ETLM’ is coded as ‘50’, then ‘YZNP’ will definitely be coded as ‘81’.

Explanation:

The given code is the addition of the positions of letters in forward alphabetical sequence.

Similarly,

code for ?YZNP?:

Note: Remember positions of letters from Table 1 (Forward alphabet order).

Example 2

If ‘A’ is coded as ‘26’, then ‘Z’ will definitely be coded as ‘1’.

Explanation:

Here, letters have been coded according to the positions of letters in backward alphabetical order. In backward alphabetical order ‘A’ has ‘26’ position. In the same way ‘Z’ has ‘1’ position in backward alphabetical sequence.

Note: Remember positions of letters from ‘Table 2’ (Backward alphabet sequence).

• If ‘EF’ is coded as ‘1’, then find the code for ‘AM’,

(a) 12                               (b) 22

(c) 21                               (d) 26

(e) None of these

Answer (a)

Explanation: Option (a) is correct because the given code of ‘EF’ is the difference in the positions of ‘E’ and ‘T’ in backward alphabetical sequence (Table 2).

‘AM’ will be coded in the same way.

Let us see:

Code for ?EF?:

Similarly,

Code for ?AM?:

Clearly, code for ‘AM’ = ‘12’.

Rest of the options is incorrect because of the correctness of option (A).

• If code for ‘ADHI’ = ‘1489’, then code for ‘GIEC’?

(a) 7953                        (b) 7935

(c) 7593                         (d) 7945

(e) None of these

Answer (a)

Explanation: Option (a) is correct because ‘A’, ‘D’, ‘H’ and ‘I’ have been replaced by their positions in forward alphabetical sequence (Table 1). ‘GIEC’ will be coded in the same way.

Let us see:

Code for ‘ADHI’:

 A D H I 1 4 8 9

Similarly,

Code for ‘GIEC’:

 G I E C 7 9 5 3

Rest of the options is incorrect because of the correctness of option (A).

Coding - Decoding Based on Fictions Language

In such problems, fictitious language is used to code some words. Fictitious codes are given for words and code for each word can be found out by eliminating the common word.

Example 1

In a certain code language ‘India is winner’ is written as ‘ba ga ra’ and ‘beautiful India’ is written as ‘ba ka’. Therefore, code for ‘India’ will definitely be ‘ba’.

Explanation:

is winner? =   ga ra?

'beautiful =   ka?

Clearly, ‘India’ is common in both and the common code is ‘ba’

$\therefore$ code for ‘India’ must be ‘ba’

Also, code for 'is' = ‘ga’ or ‘ra’

code for ‘winner’ = ‘ga’ or ‘ra’

code for ‘beautiful’ = ‘ka’

Example 2

In a certain code language ‘don’t wait long’ is written as ‘pu lu su’ and 'wire is long' is written as ‘tu nu pu’. Therefore, code for ‘long’ will definitely be ‘pu’.

Explanation:

'dont wait  =   lu su'

'wire is tu nu

Clearly, ‘long’ is common in both and a common code is ‘pu’ Therefore, code for = ‘pu’

Also, code for ‘dont’ = ‘lu’ or ‘su’

code for ‘wait’ = ‘lu’ or ‘su’

code for ‘wire’ = ‘tu’ or ‘nu’

code for Is’ = ‘tu’ or nu’

Note: In place of fictitious language you may see digits, letters and symbols also.

Commonly Asked Questions

• In a certain code language ‘you can dance’ is written as ‘ca ba ja’ and ‘dance was nice’ is written as ‘du ku ja’. What is the code for ‘dance’?

(a) ja                             (b) du

(c) ku                            (d) ba

(e) None of these

Answer: (a)

Explanation: Option (a) is correct.

Let us see:

'you can  = 'ca ba

was nice' = 'du ku

Clearly, ‘dance’ is common in both and common code for ‘dance’ is ‘ja’.

$\therefore$ code for ‘dance’ must be ‘ja’.

Rest of the options is incorrect because of the correctness of option (A).

• In a particular code language ‘water is hot’ is written as ‘914’, and ‘hot tea’ is written as ‘47’. Find the code for ‘hot’.

(a) 7                                          (b) 4

(c) 9                              (d) 1

(e) None of these

Answer: (b)

Explanation: Option (b) is correct.

Let us see:

?water is  = ?91

tea? =  7?

Clearly, code for ‘hot’ = ‘4’.

Rest of the options is incorrect because of the correctness of option (B).

Coding - Decoding Based on Words in a Chain

In such problems, more than one word make a sequence so that 1st word is the code of 2nd; 2nd word is the code of 3rd; 3rd word is the code of 4th and so on.

If ‘Red’ is called ‘Green’; ‘Green’ is called ‘Blue’; ‘Blue’ is called ‘White’; ‘White’ is called ‘Black’, then colour of peeled banana will be ‘Black’.

Explanation:

Original colour of ‘Peeled banana’ = ‘White’ In the given code ‘White’ is called ‘Black’.

Clearly, the colour of ‘Peeled banana’ will be ‘Black’.

Example 2

If ‘Apple’ is called ‘Orange’; ‘Orange’ is called ‘Banana’; ‘Banana’ is called ‘Watermelon’; then ‘Watermelon’ will be long shaped fruit.

Explanation:

As we know, that ‘Banana’ is long shaped fruit. Here, ‘Banana’ is coded as ‘Watermelon’.

Therefore, clearly, ‘Watermelon’ will be the long shaped fruit.

Commonly Asked Questions

Is If ‘White’ is called ‘Violet’; ‘Violet’ is called ‘Green’; ‘Green’; is called ‘Blue’; and ‘Blue’ is called ‘Red’, then what is the colour of ‘Eggs’?

(a) Red                          (b) Violet

(c) White                        (d) Green

(e) None of these

Answer (b)

Explanation: Option (b) is correct because colour of ‘Eggs’ is ‘White’. Here ‘White’ is called ‘Violet’. Therefore, colour of ‘Eggs’ must be ‘Violet’.

Rest of the options is incorrect because of the correctness of option (B).

• If ‘Math’ Is ‘Physics’; ‘Physics’ is called ‘History; ‘History’ is which subject of king Akbar?

(a) Maths                       (b) Physics

(c) History                      (d) Hindi

(e) None of these

Answer (d)

Explanation: Option (d) Is. correct because ‘Akbar’ story is the story of ‘History’ but here, ‘History’ is called ‘Hind’. Therefore, clearly, ‘Hindi’ contains the story of ‘Akbar’.

Rest of the options is incorrect because of the correctness of option (D).

Commonly Asked Questions

• If ‘OPEF’ is coded as ‘PQJK’, then find the code of ‘TPDL’.

(a) 1QQU                      (b) QSQU

(c) QUIQ                       (d) UQIQ

(e) None of these

Answer (c)

Explanation: Option (c) is correct because 1st two letters are coded one letter forward while last two letters are coded 5 letters forward.

Let us see:

Code for ?OPEF?:

Similarly,

Code for ?TPDL?:

Rest of the options is incorrect because of the correctness of option (C).

• Code for ‘LDNPF’ = ‘IBLNC’; code for ‘PTRCX’ = ‘?’

(a) MRPAU                    (b) MPRAU

(c) MRPUA                    (d) MARPU

(e) None of these

Answer (a)

Explanation: Option (a) is correct because three middle letters are coded two letters backward while extreme letters are coded three letters backward. Hence, ‘PTRCX’ will be coded in the same manner.

Let us see:

Code for ?LDNPF?:

Similarly,

Code for ?PTKCX?:

Clearly, code for ‘PTRCX’ = ‘MRPAU’.

Rest of the options is incorrect because of the correctness of option (A).

• If ‘TORTURE’ is coded as ‘ERUTROT’, then ‘NATURAL’ is coded as.

(a) LARUTNA                (b) LRAUTAN

(c) LARTUAN                 (d) LARUTAN

(e) None of these

Answer: (d)

Explanation: Option (d) is correct because here ‘TORTURE’ gets reversed as ‘ERUTROT’. Similarly, letters of ‘NATURAL’ will get reversed as 'LARUTAN'.

Rest of the options is incorrect because of the correctness of option (D).

• If 'PMQE' is coded as '51', then how will 'NRSZ' be coded?

(a) 105                                      (b) 85

(c) 98                                        (d) 77

(e) None of these

Answer (d)

Explanation: Option (d) is correct because addition of the letter positions in forward order has been made code here. Therefore, 'NRSZ' will also be coded in the same manner.

Let us see:

Code for ?PMQE?:

Similarly,

Code for ?NRSZ?:

Rest of the options is incorrect because of the correctness of option (D).

• If ‘Tiger’ is called ‘Cow’, ‘Cow’ is called ‘Lion’; ‘Zion’ is called 'Panther', and 'Panther' is called 'Goat' then .......... is a domestic animal.

(a) Book                        (b) Pen

(c) Lion                         (d) Tiger

(e) None of these

Answer (c)

Explanation: Option (c) is correct because it is a well-known fact that ‘Cow’ is a domestic animal. But here 'Cow' is called 'Lion'. Therefore, clearly, in this case domestic animal is 'Lion'.

Rest of the options is incorrect because of the correctness of option (C).

Summary

• Coding is a system of words, letters, numbers etc. used in place of ordinary writing to keep something secret.
• While solving coding-decoding problems, students must keep in mind the positions of
• English letters in forward and backward order. (See ‘Table 1’ and ‘Table 2’).
• Students must have the knowledge of opposite letters in English alphabet. (See 'Table 3')

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##### Notes - Coding-Decoding

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