Page 60 - Math Skill - 4

58 Maths

Prime Numbers
A number that has exactly two factors, 1 and the number itself is called a prime number.

For example, Factors of 2 are 1 and 2. Thus, 2 is a prime number.

Factors of 3 are 1 and 3. Thus, 3 is a prime number.
Composite Numbers

A number having more than two factors is called a composite number.

For example, Factors of 4 are 1, 2 and 4. Thus, 4 is a composite number.
Factors of 6 are 1, 2, 3 and 6. Thus, 6 is a composite number.

Fact-o-meter
� All numbers except 1 and 0 are either prime or composite numbers.
� 2 is the only even and the smallest prime number.

Prime Factorisation

Now, when we know the concept
of prime numbers and the factors, 32
we can learn the process of prime
factorisation. Prime factorisation 2 × 16 32
is writing a number as a product
of all the factors that are prime 2 × 8 4 × 8
numbers. Here, the factor tree
can help us in understanding 2 × 4 2 × 2 2 × 4
it in a better way. Let us take a
number 32 and this number can 2 × 2 2 × 2
be branched out in different ways.
As you can see the result is same 32 = 2 × 2 × 2 × 2 × 2 32 = 2 × 2 × 2 × 2 × 2
in both the cases.

Similarly, factor trees for 56 are as shown below:

56 56

7 × 8 2 × 28
56

2 × 4 7 × 4 4 × 14

2 × 2 2 × 2 2 × 2 2 × 7

56 = 2 × 2 × 2 × 7 in all the cases.