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# Exercise 7.3 (Cryptology)

8th Maths : Chapter 7 : Information Processing : Cryptology : Exercise 7.3 : Text Book Back Numerical problems, Exercises Questions with Answers, Solution

Exercise 7.3

1. Fill in the blanks (Use Atbash Cipher that is given in code 3)

Solution:

For this question, we need to use Atbash cipher. For Atbash cipher, first we write the alphabets from A to Z and then in reverse from Z to A below that.

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

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

(i) G Z N R O = _____________________________

Solution:

Now to solve, we look up the corresponding letter from the table to replace in code to get the actual word.

So, for G Z N R O, from table,

for G, it is T

for Z, It is A

for N, it is M

for R, it is I

for O, it is L

So , the actual word is TAMIL

(ii) V M T O R H S = _____________________________

Solution:

V M T O R H S

To solve, we look up the corresponding letter from table to replace in code to get the actual word.

For V, it is E

for M, it is N

for T, it is G

for O, it is L

for R, it is I,

for H, it is S

for S, it is H

Therefore we get E N G L I S H = ENGLISH

(iii) N Z G S V N Z G R X H = _____________________________

Solution:

Similarly as above for

= MATHEMATICS

(iv) H X R V M X V = _____________________________

Solution:

For

(v) H L X R Z O H X R V M X V = _____________________________

Solution:

For

2. Match the following ( a = 00……………. Z= 25).

(i) mathematics - (a) 18 20 01 19 17 00 02 19 08 14 13

(ii) addition - (b) 03 08 21 08 18 08 14 13

(iii) subtraction - (c) 12 00 19 07 04 12 0019 08 02 18

(iv) multiplication - (d) 00 03 03 08 19 08 14 13

(v) division - (e) 12 20 11 19 08 15 11 15 02 00 19 08 14 13

[Answer: i − c, ii − d, iii − a, iv − e, v – b ]

Solution:

Given that the code is

Solution:

(i) Mathematics is

So matching option is c

Matching option is d

(iii) Subtraction is

Matching option is a

(iv) multiplication is

Matching option is e

however instead of 25, it should be 08

(v) division is

Matching option is b

3. Frame Additive cipher table (key = 4).

Solution:

Step 1 : write all alphabets

Step 2 : Assign numbers to each alphabet starting from 00 till 25.

Step 3 : add key value (here it is 4) to the numbers assigned in step 2 to form cipher table

4. A message like “Good Morning” written in reverse would instead be “Doog Gninrom”. In the same way decode the sentence given below:

“Ot dnatsrednu taht scitamehtam nac eb decneirepxe erehwreve ni erutan dna laer efil.”

Solution:

Given that good morning written in reverse is doog gninrom.

We have to decode the below by reversing, so,

Ot dnatsrednu taht scitamehtam nac eb decneirepxe erehwreve ni erutan dna laer efil.

To understand that mathematics can be experienced everywhere in nature and real life.

5. Decode the given Pigpen Cipher text and compare your answer to get the Activity 3 result.

I. The room number in which the treasure took place:

II. Place of the treasure :

III. The name of the treasure :

Solution:

(i) The room in which the treasure took place = 28

(ii) The place of treasure = CHAIR

(iii) Identity of treasure = GIFT VOUCHER.

6. Praveen recently got the registration number for his new two-wheeler. Here, the number is given in the form of mirror-image. Encode the image and find the correct registration number of raveen’s two-wheeler.

Solution:

The mirror image is

When we place an imaginary mirror & visualize the image seen in the mirror, we will get the below.

The answer uis Option c

Objective Type Questions

7. In questions (i) and (ii), there are four groups of letters in each set. Three of these sets are alike in some way while one is different. Find the one which is different.

(i). (A) C R D T (B) A P B Q (C) E U F V (D) G W H X

(ii). (A) H K N Q (B) I L O R (C) J M P S (D) A D G J

[ Answer: (i). (A) C R D T (ii). (D) A D G J]

Solution:

A. The four groups of letters are

CRDT  APBQ  EUFV  GWHX

The above can be written as

We find that when we take 1st & 3rd letter & 2nd & 4th letter as 2 pairs, the 3rd letter is the next letter alphabetically to the lst letter.

Similarly the 4th letter is alphabetically the next letter of the 2nd letter.

i.e CD, AB, EF, GH & PQ, UV, WX

Only in CRDT, we have T instead of 'S'

So, Answer: in CRDT Option (A)

B. The four groups of letters are

HKNQ ILOR JMPS ADGI

If we notice, we find that 2 letters are missing in the sequence, ie.

HIJKLMNOPQ     IJKLMNOPQR

JKLMNOPQRS       ABCDEFGHI

We find that only in ADGI, the difference is only one letter between G & I.

Hence it is the odd one out.

8. A group of letters are given. A numerical code has been given to each letter. These letters have to be unscrambled into a meaningful word. Find out the code for the word so formed from the 4 answers given.

(A) 234156

(B) 563421

(C) 613524

(D) 421356

[Answer: (B) 5 6 3 4 2 1 ]

Solution:

Given code is

Option (a) is 234156. When we substitute number for each letter from code, we get,

So, only in option b, we get a meaningful word, i.e PENCIL.

Hence, answer is Option b)

9. Questions (iii) and (iv) are based on code language. Find the correct answer from the four alternatives given.

(iii) In a certain code, ‘M E D I C I N E’ is coded as E O J D J E F M’, then how is ‘C O M P U T E R’ written in the same code ?

(A)CNPRVUFQ

(B)CMNQTUDR

(C)RFUVQNPC

(D)RNVFTUDQ

[Answer: (C) R F U V Q N P C]

Solution:

It is given that in a certain code M E D I C I N E is coded as E O J D J E F M

When we observe the word & the code, we find that, there is a pattern.

[ to understand, see the matching shapes]

To get the code from the word, we follow the below steps

1.  M E D I C I N E swap 1st & last letters, so we get

E [ E D I C I N ] M

2. For the middle letters, replace the letters with their alphabetically next letters, so we get

3. Now we have to reverse the order of the middle letters in the bracket, so we get

E [O J D J E F ] M = E O J D J E F M

Thus we get the code.

So similarly, we have to follow the 3 steps to get code, therefore :

for

Step 1: Swap 1 st & last letters, so we get

R [ O M P U T E ] C

Step 2: For the middle letters, replace the letters with alphabetically next letters, so we get

[ P N Q V U F ] C

Step 3: Reverse the word of letters in the bracket to we get

R [ F U V Q N P ] C

Ans is R F U V Q N P C Option C

(iv) If the word ‘P H O N E ’ is coded as ‘S K R Q H’, how will ‘R A D I O’ be coded ?

(A) S C G N H

(B) V R G N G

(C) U D G L R

(D) S D H K Q

[Answer: (C) U D G L R]

Solution:

If PHONE is coded as S K R Q H

Find that code for R A D I O

We find that we get the code, by 3rd letter alphabetically so, from P, skipping Q & R, we get S.

Similarly, from H, skipping I & J, we get K

Like wise for R A D I O, skipping the 2 alphabets,

From R, skip S & T → U

From A, skip B & C → D

From D skip E & F →  G

From I skip J & K → L

From O skip P & Q → R

Ans. is UDGLR Option c

Exercise 7.3

1. (i) TAMIL (ii) ENGLISH (iii) MATHEMATICS (iv) SCIENCE (v) SOCIAL SCIENCE

2 (i) c (ii) d (iii) a (iv) e (v) b

3 .

4. To understand that mathematics can be experienced everywhere in nature and real life.

(i) 28 (ii) CHAIR (iii) GIFT VOUCHER

6. (c)

7. (i) (a) C R D T (ii) (d) A D G J

8. (ii) 5 6 3 4 2 1

9. (i) (c) R F U Q N P C (ii) (c) U D G L R

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