Page 192 - New Medley 4 Semester 1

Example 11: Identify the odd and even numbers in each of the
following.

(a) 17 (b) 20 (c) 23 (d) 62

Solution: (a) As 17 ÷ 2 = 8 + 1 (remainder), so, 17 is odd.
(b) As 20 ÷ 2 = 10, so, 20 is even.

(c) As 23 ÷ 2 = 11 + 1 (remainder), so, 23 is odd.

(d) As 62 ÷ 2 = 31, so, 62 is even.

Prime and Composite Numbers

Prime Numbers

The numbers which have only two factors 1 and itself are called prime

numbers.

Composite Numbers

The numbers which have more than two factors are called composite

numbers.

Let us investigate the factors of the numbers from 1 to 20 and categorise
them into primes and composites.

Numbers Factors Primes (P)/Composites (C)

1 1 Neither P nor C

2 1, 2 P

3 1, 3 P

4 1, 2, 4 C

5 1, 5 P

6 1, 2, 3, 6 C

7 1, 7 P

8 1, 2, 4, 8 C

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