Page 41 - Revised Maths Wisdom Class - 6

Prime Time 39

ILLUSTRATIONS

Example 1: Find the first three common multiples of 3, 5 and 15.
Solution: Multiples of 3 = 3, 6, 9, 12, 15 , 18, 21, 24, 27, 30 , 33, 36, 39, 42, 45 , 48, ...

Multiples of 5 = 5, 10, 15 , 20, 25, 30 , 35, 40, 45 , 50, ...

Multiples of 15 = 15 , 30 , 45 , 60, ...
The common multiples are 15, 30, 45, so on.

Example 2: Write the common factors of 8, 20, 36.
Solution: Factors of 8 = 1, 2, 4, 8
Factors of 20 = 1, 2, 4, 5, 10, 20
Factors of 36 = 1, 2, 3, 4, 6, 9, 12, 18, 36
The common factors of 8, 20 and 36 are 1, 2, and 4.

Exercise 3A
Exercise 3A
1. Find first five multiples of:
(a) 11 (b) 37 (c) 16 (d) 43 (e) 87
2. Write all the factors of:
(a) 60 (b) 85 (c) 96 (d) 175 (e) 276
3. Write all the common multiples of 7 and 5 from 1 to 100.

4. Find the first three common multiples of:
(a) 4 and 6 (b) 2, 3 and 4 (c) 3 and 11
5. Write the common factors of:
(a) 70 and 125 (b) 63 and 153 (c) 46 and 64

6. Write the multiples of 3 between 71 and 93.
7. A gardener has 60 orchid bulbs. He wants to plant them in rows and columns in the garden. What are the
different ways to do so?
8. Check whether 10 is a perfect number or not.

Types of Numbers

Even and Odd Numbers
The numbers which are completely divisible by 2 are called even numbers. For example, 2, 4, 6, 8, 10, 12, 14, etc.
are even numbers. An even number always ends with 0, 2, 4, 6 or 8.
The numbers that are not even are odd numbers. These numbers are not divisible by 2. For example, 13, 17 and
331 are odd numbers. An odd number always ends with 1, 3, 5, 7 or 9.

Prime and Composite Numbers
Those numbers having exactly two factors, 1 and the number itself are called prime numbers. For example, 2, 3,
5, 7, 11, 13, 17, 19, ... are all prime numbers.
Numbers having more than two factors are called composite numbers. For example, 4, 6, 8, 9, 12, 15, ... are all
composite numbers.