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 = _____________________________**

**[Answer: TAMIL]**

**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 = _____________________________**

**[Answer: ENGLISH]**

**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 = _____________________________**

**[Answer: MATHEMATICS]**

**Solution:**

Similarly as above for

= MATHEMATICS

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

**[Answer: SCIENCE]**

**Solution:**

For

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

**[Answer: SOCIAL SCIENCE]**

**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

**(ii) addition is**

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.**

**Answer:**

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 1^{st} & 3^{rd}
letter & 2^{nd} & 4^{th} letter as 2 pairs, the 3^{rd}
letter is the next letter alphabetically to the l^{st} letter.

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

H_{IJ}K_{LM}N_{OP}Q I_{JK}L_{MN}O_{PQ}R

J_{KL}M_{NO}P_{QR}S A_{BC}D_{EF}G_{H}I

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

R [ 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 3^{rd} 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

**Answer:**

**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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8th Maths : Chapter 7 : Information Processing : Exercise 7.3 (Cryptology) | Questions with Answers, Solution | Information Processing | Chapter 7 | 8th Maths

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