๐ QUICK CHAPTER NOTES
๐น Prime Numbers
A prime number has exactly 2 factors:
๐ 1 and the number itself
โ Examples
2, 3, 5, 7, 11, 13โฆ
โญ Important Points
- 2 is the only even prime number
- All other primes are odd numbers
๐น Composite Numbers
A composite number has more than 2 factors
โ Examples
4, 6, 8, 9, 10, 12โฆ
๐น Special Case
๐ 1 is neither prime nor composite
๐น Key Understanding
- Prime = cannot be broken into smaller factors
- Composite = can be broken into smaller factors
๐น How to Check Prime?
๐ Check divisibility from 2 up to โnumber (basic level: try small numbers)
๐ WORKSHEET โ PRIME & COMPOSITE NUMBERS
๐น SECTION A (Very Short Answer)
- Write first 5 prime numbers.
- Write first 5 composite numbers.
- Is 1 a prime number?
- Smallest prime number
- Smallest composite number
- Is 2 prime or composite?
- Is 9 prime or composite?
- Write any two prime numbers.
- Write any two composite numbers.
- How many factors does a prime number have?
๐น SECTION B (Identify Prime/Composite)
- 13
- 15
- 17
- 21
- 23
- 25
- 29
- 33
- 37
- 39
๐ Write whether each is Prime / Composite
๐น SECTION C (List-Based Questions)
- Write all prime numbers between 10 and 30
- Write all composite numbers between 10 and 20
- Write all even prime numbers
- Write all odd composite numbers less than 20
- Write all prime numbers less than 15
๐น SECTION D (Reasoning Based)
- Why is 2 the only even prime number?
- Why is 1 neither prime nor composite?
- Can a prime number have more than 2 factors?
- Can a composite number have exactly 2 factors?
- Which is greater: number of factors of a prime or composite number?
๐ฅ SECTION E โ CASE-BASED QUESTIONS
๐ Case Study 1: Number Cards
A student has cards: 2, 4, 5, 6, 7
- Which are prime numbers?
- Which are composite numbers?
- Which is the only even prime number?
๐ Case Study 2: School Activity
A number 21 is chosen.
- Write its factors
- Is it prime or composite?
- Why?
๐ Case Study 3: Puzzle Number
A number has factors 1 and 19 only
- Identify the number
- Is it prime or composite?
- Give reason
๐ Case Study 4: Grouping Game
A teacher wants to form equal groups using 7 students.
- Can 7 be divided into equal groups other than 1 and itself?
- Is 7 prime or composite?
๐ Case Study 5: Number Challenge
- Write a prime number between 20 and 25
- Write a composite number between 20 and 25
- Write a 2-digit prime number
- Write a 2-digit composite number
- Which is the smallest odd prime number?
- Which is the smallest odd composite number?
- Write two consecutive prime numbers
- Can 15 be a prime number? Why?
- Write all prime numbers between 1 and 10
โ ANSWER KEY
SECTION A
- 2,3,5,7,11
- 4,6,8,9,10
- No
- 2
- 4
- Prime
- Composite
- Example: 3,5
- Example: 6,8
- 2
SECTION B
- Prime
- Composite
- Prime
- Composite
- Prime
- Composite
- Prime
- Composite
- Prime
- Composite
SECTION C
- 11,13,17,19,23,29
- 12,14,15,16,18
- 2
- 9,15
- 2,3,5,7,11,13
SECTION D
- Because all other even numbers have more than 2 factors
- Because it has only 1 factor
- No
- No
- Composite numbers
SECTION E
- 2,5,7
- 4,6
- 2
- 1,3,7,21
- Composite
- More than 2 factors
- 19
- Prime
- Only 2 factors
- No
- Prime
- 23
- 21 or 24
- 11
- 12
- 3
- 9
- 3,5
- No (more than 2 factors)
- 2,3,5,7
