1. NUMBER SYSTEM
(PART-2)
We are going to study NATURAL NUMBERS in detail in this
presentation(ppt).
Types of Natural Numbers –
UNIQUE NUMBER
PRIME NUMBER
COMPOSITE NUMBER
2. NATURAL NUMBER
• Counting numbers starting from 1 are Natural numbers.
• Ex : 1,2,3,4,5,6,7,8,9,10……………………………………………
• 3 types of Natural numbers –
Unique Number, Prime Number, Composite Number
UNIQUE NUMBER : -
- 1 is Unique Number.
- 1 is neither prime nor composite.
- 1 has only one factor, i.e, the number 1 itself.
3. PRIME NUMBER :-
• Has only 2 factors: 1 and itself.
• Ex:- 2,3,5,7,11,13,17,19,23,29………………………………….
• Factors of 2 - 1 and 2 (only 2 factors)
• Factors of 3 - 1 and 3 (only 2 factors)
• Factors of 5 - 1 and 5 (only 2 factors)
• Factors of 11 - 1 and 11 (only 2 factors)
• Factors of 47 - 1 and 47 (only 2 factors)
NOTE – 2 is the only even prime number. (Important)
4. COMPOSITE NUMBER :
• Has more than 2 factors
• Ex:- 4,6,8,9,10,12,14,15,16,18,20,22 ………………………..
• Factors of 4 : 1,2,4 (3 factors)
• Factors of 6 : 1,2,3,6 (4 factors)
• Factors of 8 : 1,2,4,8 (4 factors)
• Factors of 9 : 1,3,9 (3 factors)
All the above numbers are having more than 2 factors, hence they
are composite numbers.
5. Question:- How many Prime numbers are below 50.
Answer :- There are 15 Prime numbers below 50.
Following are the prime numbers below 50-
2,3,5,7,11,13,17,19,23,29,31,37,41,43,47
The above numbers are having only 2 factors : 1 and itself,
Hence they are prime numbers.
6. Question:- How many composite numbers are below 50.
Answer : There are 33 composite numbers below 50.
- 1 is unique number.
- In the previous example we have seen that there are 15 prime
numbers below 50.
- Total number of natural numbers below 50 = 49
- Hence total number of composite numbers below 50 = 49-(1+15)
= 33
