Page 187 - Start Up Mathematics_4

Coding and Decoding

Numbers and letters together with pictures can also be used for coding and decoding
messages. Look at the given example to understand this better.

Example 9: Shonali messages her phone number to her friend. The number is EUTIHZPI.
Decode it using the given codes to get Shonali’s number.
0 1 2 3 4 5 6 7 8 9

↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓
Z A E I O U H P R T

Solution: Shonali’s phone number is 25936073.

EXERCISE 13.7

1. Complete the given patterns.

(a) 3, 5, 8, 12, 17, _______, _______, _______, _______
(b) 1, 1, 2, 6, 24, _______, _______, _______, _______

(c) 10, 20, 35, 55, 80, _______, _______, _______, _______
2. Tick the option that makes the pattern true.

(a) 48 ÷ 8 = x (i) x = 6, y = 48, z = 600

y ÷ 8 = 60 (ii) x = 60, y = 480, z = 60
4800 ÷ 8 = z (iii) x = 6, y = 480, z = 600

(b) 80 ÷ x = 40 (i) x = 2, y = 20, z = 320

80 ÷ 4 = y (ii) x = 20, y = 4, z = 400
z ÷ 8 = 40 (iii) x = 2, y = 20, z = 800

3. (a) Use the following codes to code the given messages.

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
(i) Keep your city clean. (ii) Respect your elders.

(b) Now decode these messages.

(i) 18 15 12 5 22 14 2 24 12 6 13 7 9 2
(ii) 8 26 5 22 4 26 7 22 9 26 13 23 22 15 22 24 7 9 18 24 18 7 2
(iii) 19 26 11 11 2 23 18 4 26 15 18

179