# 5th Class Mental Ability Coding-Decoding Coding Decoding

Coding Decoding

Category : 5th Class

Coding - Decoding

Learning Objective

• To get aware of coding – decoding.
• Improving the logical ability.
• To be perfect in solving problems.

What is Coding-Decoding?

Let us start it with an interesting story.

Suppose you and your papa like ice-cream very much. But your mummy does not want you two to have it because you both catch cold very easily. Then you and your papa make a secret plan to use the word 'Chocolate’ for ice-cream. Now, whenever you feel like eating ice-cream you say to your papa that you want to eat chocolates. Mummy hears it and thinks that you are really demanding chocolates. Therefore, she gives you permission to go out with papa and enjoy chocolates. Then you and your papa go out, eat ice-cream and comeback.

Do you think what happens here? Here, you coded the word 'Ice-cream' with another word 'Chocolate'. Only you and papa know about this code, when you say that you want to eat 'Chocolate' then your papa hears you and easily decodes it that you want to eat ice-cream. This can be presented as below.

Ice-cream $\xrightarrow{Coded\,\,as}$ Chocolate $\xrightarrow{Decoded\,\,as}$ Ice-cream

How to Decode?

In reasoning, words, letters and numbers are coded according to a certain rule. While solving problems, students have 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, you 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:

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

Table 2:

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

Opposite letters

Table 3:

 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

(a) Coding - Decoding In Forward Sequence

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

Example 1:    If 'AB' is coded as 'BC’, then 'EF’ will definitely be coded as ‘FG’.

Explanation:   Here, letters of ‘AB’ shift one place in forward alphabetical sequence.

Similarly, letters of ^EF shift one place in forward alphabetical order.

Let us see:

Clearly, code for 'AB' is ‘BC’ and code for ‘EF’ is ‘FG’.

Example 2:    If 'GO' is coded as IQ', then 'TO' will definitely be coded as 'VQ’.

Explanation:   Here, letters of the word ‘GO’ shift two places in forward alphabetical sequence.

Let us see:

Similarly, both letters of the word ‘TO’ will move two places forward.

Let us see:

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

1. If code of 'LMN' = 'MNO', then find the code for 'PQR'.

(a) QRS                        (b) RQP

(c) SRQ                         (d) QSR

(e) None of these

Explanation: Option (a) is correct because in this case Setters are coded one place forward.

Let us see:

LMN

Code for 'LMN':

Similarly,

Code for 'PQR':

Clearly, code for 'PQR' is 'QRS'.

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

1. If 'TWO’ is coded as 'VYQ', then 'NEW’ will be coded as_ _ _ _ _

(a) WEN                                    (b) PGY

(c) YPG                                     (d) GPY

(e) None of these

Explanation: Option (b) is correct because in this case letters are coded two places forward.

Let us see:

Code for 'TWO’:

Similarly,

Code for 'NEW’:

Clearly, code for 'NEW' is 'PGY'.

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

(b)    Coding - Decoding In Backward Sequence

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

Example 1:    If ‘LM’ is coded as ‘KL’, then DE will definitely be coded as ‘CD’.

Explanation:   Here, letters of 'LM' are coded one place backward.

Let us see:

Similarly, both letters of 'DE' are coded one place backward.

Let us see:

Clearly, code for ‘DE’ is 'CD'.

Example 2:    If 'ROSE' is coded as 'PMQC', then 'NOSE' will definitely be coded as 'LMQC'.

Explanation:   Here, letters of 'ROSE' are coded two places backward.

Let us see:

In the same manner, letters of 'NOSE' are coded two places backward.

Let us see:

Clearly, code for 'NOSE' is 'LMQC'.

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

1. If code for 'SO' is 'QM', then what will be the code for 'GH'?

(a) MQ                                      (b) FG

(c) FE                                        (d) EF

(e) None of these

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

Let us see:

Code for 'SO':

Similarly,

Code for 'GH':

Clearly, code for ‘GH’ is 'EF’.

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

2. If 'DIE' is coded as CHD', then 'NET' will be coded as _ _ _ _ _

(a) MDS                                    (b) TEN

(c) UFO                                     (d) SDM

(e) None of these

Explanation: Option (a) is correct because in this case letters are coded one place backward.

Let us see:

Code for ‘DIE’:

Similarly,

Code for 'NET? is ?MDS?.

Clearly, code for 'NET’ is 'MDS'.

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

(c)   Coding - Decoding In Forward - Backward Sequence

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

Example 1:    If ‘PQ’ is coded as ‘RO’, then 'CD’ will definitely be coded as ‘EB’.

Explanation:   Here, in ‘PQ' P is coded 2 places forward and Q is coded 2 places backward.

Let us see:

Similarly, in ?CD?, C is coded two places forward and D is coded two places backward.

Let us see:

Clearly, code for 'CD' is 'EB'

Example 2:    If 'NAME' is coded as 'MBLF', then 'GAME' will definitely be coded as 'FBLF'.

Explanation:   Here, letters are coded one place backward and one place forward alternately.

Let us see:

Similarly,

Code for 'GAME':

Clearly, code for 'GAME' is TBLF'.

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

1. If 'EF' is coded as 'CH', then 'LT' will be coded as..............

(a) TL                           (b) UM

(c) JV                           (d) VJ

(e) None of these

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

Let us see:

Code for 'EF’:

Similarly,

Code for 'LT':

Clearly, code for 'LT' is 'JV’.

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

1. If 'SHOW is coded as 'TGPV, then how will 'NINE' be coded?

(a) OHOD                      (b) DOHO

(c) HOOD                      (d) DOOH

(e) None of these

Explanation: Option (a) is correct because letters are coded 1 place forward and one place backward alternately.

Let us see:

Code for 'SHOW:

Similarly,

Code for 'NINE':

Clearly, code for 'NINE' is 'OHOD'.

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

(d)    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 'ABC' is coded as 'CBA', then 'TGP' will definitely be coded as 'PGT'.

Explanation:   'ABC' is coded in reverse order as

'CBA'

Similarly, 'TGP' will be coded by writing the letters in reverse order.

Therefore, the code for 'TGP' will be 'PGT'.

Example 2:    If 'KIND' is coded as 'DNIK' then 'MIND' will definitely be coded as 'DNIM'.

Explanation:   'KIND' is coded in reverse order as 'DNIK'. In the same way the code for 'MIND' has been obtained by writing it in reverse order as 'DNIM'.

1. Code for 'NAME' = 'EMAN', then code for 'GAME' = '?'

(a) MAGE                                  (b) EMAG

(c) AGME                                  (d) GMEA

(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).

1. If 'NOPE' is coded as 'EPON', then 'NOSE' will be coded as..............

(a) SEON                                   (b) ONSE

(c) NSEO                                   (d) ESON

(e) None of these

Explanation: Option (d) is correct because here, the letters of given word 'NOPE' has been coded by writing them in reverse order Following the same pattern, the code for 'NOSE' will be 'ESON'.

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

(e)   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 ‘2’; 'B' is coded as 3’; 'C' is coded as '4' and so on, then code for 'AECB' will definitely be '2643'.

Explanation:   In this case, letters are coded as below:

 A B C D E F ? ? ? 2 3 4 5 6 7 ? ? ?

Now,

 A E C B 2 6 4 3

Clearly, the code for 'AECB' is '2643'.

Example 2:    In a certain code, '3' is coded as 'P'; '4' is coded as 'R'; '5' is coded as 'D'; '6' is coded as 'T' then the code for '55364' will definitely be 'DDPTR'.

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

 3 4 5 6 P R D t

Now,

 5 5 3 6 4 D D P T R

Clearly, the code for '55364' is 'DDPTR'.

1. Just see the following letter codes and find the code for ‘RGP'.

 A P T G R 5 6 9 1 2

(a) 216                         (b) 316

(c) 612                          (d) 126

(e) None of these

Explanation: Option (a) is correct.

 R G P 2 1 6

Clearly, code for 'RGP' is '216'.

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

2. In a certain code language '3' is coded as 'D'; '4' is coded as 'W; '5' is coded as N. Then how will 'NND' be coded?

(a) 455                                      (b) 545

(c) 453                                      (d) 553

(e) None of these

Explanation: Option (d) is correct.

 N N D 5 5 3

Clearly, code for 'NND' is '553'.

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

(f)     Opposite Letters Coding’ Decoding

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

Example 1:    If 'AB' is coded as ‘ZY’, then ‘FG' will definitely be coded as UT.

Explanation:   ‘A’ is opposite letter of 'Z' and ‘B’ is opposite letter of ‘Y’. Similarly, ‘F' is opposite letter of ‘U’ and ‘G’ is opposite letter of ‘T’ Hence, based on this logic ‘FG' will be the code for 'UT’.

Example 2:    If code for I is R, then 'M’ will definitely be coded as N.

Explanation:   ‘I’ is opposite letter of ‘R’. Similarly ‘M’ is opposite letter of ‘N’.

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

1. 'Q' is coded as T, then how will V be coded?

(a) E                             (b) D

(c) M                            (d) L

(e) None of these

Explanation: Option (a) is correct because ‘Q’ and ‘J’ are opposite letters.

Similarly, 'V will be coded by its opposite letter 'E'.

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

1. The code for 'MK' = 'NP', then code for 'EC' =‘?’

(a) XV                          (b) XL

(c) XD                          (d) VX

(e) None of these

Explanation: Option (d) is correct because

Opposite letter of 'M' = 'N'

Opposite letter of 'K' = ‘P’

Similarly, Opposite letter of ‘E’ = ‘V’

Opposite letter of 'C = 'X'

Clearly, code for 'EC ='VX'.

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

(g)    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 'AB' is coded as '3', then 'DE' will definitely be coded as '9'.

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

Let us see:

Similarly, code for 'DE':

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

Example 2:    If 'A' is coded as '26', then 'D' will definitely be coded as '23'.

Explanation:   Here, letters have been coded according to the positions of letters in backward alphabetical order. In backward alphabetical order 'A' has '26'th position. In the same way 'D' has '23'rd position in backward alphabetical sequence.

Note: Remember positions of letters from 'Table V (Backward alphabet sequence).

1. If 'HI' is coded as '1', then find the code for 'AM'.

(a) 12                           (b) 18

(c) 8                              (d) 10

(e) None of these

Explanation: Option (a) is correct because the given code of 'HI' is the difference in the positions of H and ‘I’ in          alphabetical sequence (Table 2).

‘AM’ will be coded in the same way.

Let us see:

Code for 'HI':

Similarly,

Code for 'AM':

Clearly, code for 'AM' = '12'.

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

1. If code for 'FG' = '67', then code for 'CA'?

(a) 13                           (b) 61

(c) 31                           (d) 16

(e) None of these

Explanation: Option (c) is correct because 'F' and 'G' have been replaced by their positions in forward alphabetical sequence (Table 1), 'CA' will be coded in the same way.

Let us see:

Code for 'FG':    F          G

6          7

Similarly,

Code for 'CA':    C          A

3         1

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

(h)    Coding - Decoding Based on Fictitious 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 'go and Play' is written as 'da pa ta' and 'come and do' is written as 'sa na pa'. Therefore, code for 'and' will definitely be 'pa'.

Explanation:   'go'  play' = 'da  ta'

'come' do'='sa na'

Clearly, 'and' is common in both and the common code is 'pa'.

$\therefore$ code for 'and' must be 'pa'

Also, code for 'go' = 'da' or 'ta'

code for 'play' = 'da' or 'ta'

code for 'come' = 'sa' or 'na'

code for 'do' = 'sa' or 'na'

Example 2:    In a certain code language 'eat banana' is written as 'la na' and 'yellow banana' is written as 'da la'. Therefore, code for 'banana' will definitely be 'la'.

Explanation:   'eat?  =  ?na'

'yellow  = da ?

Clearly, 'banana' is common in both and a common code is 'la'.

Therefore, code for 'banana' = 'la'

Also, code for 'eat' = 'na'

code for 'yellow' = 'da'

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

1. In a certain code language 'you are brave' is written as 'ma sa ka', and 'you and me ' is written as 'ra na ma'. What is the code for 'you'?

(a) ma                          (b) ka

(c) sa                             (d) ra

(e) None of these

Explanation: Option (a) is correct

Let us see:

' are brave'=  sa ka'

'and me'='ra na '

Clearly, 'you' is common in both and common code for 'you' is 'ma'.

$\therefore$ code for 'you' must be 'ma'.

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

2. In a particular code language 'come soon' is written as '24', and 'go soon' is written as '52'. Find the code for 'soon'.

(a) 5                             (b) 4

(c) 2                             (d) 3

(e) None of these

Explanation: Option (c) is correct.

Let us see:

'come'= 4'

'go  = '5 '

Clearly, code for 'soon' = '2'.

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

(i)    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.

Example 1:     If 'Blue' is called 'Green'; 'Green' is called 'Black'; 'Black'; is called 'White'; 'White' is called 'Red', then colour of milk will be 'Red'.

Explanation:   Original colour of 'Milk' = 'White'. In the given code 'White' is called 'Red'. Clearly, the colour of 'Milk' will be 'Red'.

Example 2:    If 'Cat' is called 'Dog'; 'Dog' is called 'Cow'; 'Cow'; is called 'Rat'; then 'Rat' will be heaviest among the given animals.

Explanation:   As we know, that 'Cow' is heavier than 'Dog' and 'Cat'. Here, 'Cow' is coded as 'Rat'. Therefore, clearly, 'Rat' will be the heaviest.

1. If 'Red' is called 'Yellow'; 'Yellow' is called 'Green'; 'Green'; is called 'Blue'; and 'Blue' is called 'Black', then what is the colour of 'Clear sky'?

(a) Pink                                     (b) Yellow

(c) Green                                   (d) Black

(e) None of these

Explanation: Option (d) is correct because colour of 'Sky' is 'Blue'. Here 'Blue' is called 'Black'. Therefore, colour of 'Clear sky' must be 'Black'.

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

1. If 'Room' is called 'Bed'; 'Bed' is called 'Earth'; 'Earth'; is called 'Sky'; then where do we sleep on?

(a) Room                                   (b) Bed

(c) Sky                                        (d) Earth

(e) None of these

Explanation: Option (d) is correct because we sleep on 'Bed' but here, 'Bed' is called 'Earth'. Therefore, clearly, we sleep on 'Earth'.

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

1. If 'TOP' is coded as 'UPQ', then find the code of 'RAT.

(a) TAR                                     (b) ART

(c) SBU                        (d) UBS

(e) None of these

Explanation: Option (c) is correct because letters of 'TOP' are coded one letter forward. Hence, 'RAT' will be coded in the same manner.

Let us see:

Code for 'TOP':

Similarly,

Code for 'RAT':

Clearly, code for 'RAT' will be 'SBU'.

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

2. Code for 'DP'=='BN'; code for 'TC'='?'

(a) RA                          (b) AR

(c) CT                          (d) NB

(e) None of these

Explanation: Option (a) is correct because letters 'D' and 'P' are coded two letters backward. Hence, 'TC' will be coded in the same manner.

Let us see:

Code for 'DP':

Similarly,

Code for 'TC':

Clearly, code for 'TC' = 'RA'.

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

3. If 'POT' is coded as 'TOP', then 'CAT' is coded as..........

(a) ACT                        (b) CTA

(c) ATC                                     (d) TAC

(e) None of these

Explanation: Option (d) is correct because here 'POT' gets reversed as 'TOP'.

Similarly, letters of 'CAT' will get reversed as 'TAC'.

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

4. If 'NO' is coded as '29', then how will 'CA' be coded?

(a) 31                           (b) 13

(c) 4                              (d) 3

(e) None of these

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

Let us see:

Code for 'NO'

Similarly,

Code for 'CA':

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

5. If 'Book' is called ‘Pen’ is called ‘Cell’ and ‘Cell’ is called ‘Copy’, then we write with a ..........

(a) Book                                     (b) Pen

(c) Copy                                     (d) Cell

(e) None of these

Explanation: Option (d) is correct because it is a well-known fact that we write with a 'Pen'. But here 'Pen' is called 'Cell’. Therefore, clearly, in this case we write with a 'Cell'.

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

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