In this Grade 4 lesson from Pengi Math Chapter 5, students learn to define and distinguish prime and composite numbers based on their number of factors. They explore why 1 is neither prime nor composite, discover that all even numbers greater than 2 are composite, and apply the Sieve of Eratosthenes to systematically identify all prime numbers up to 100.
Section 1
Defining Prime and Composite Numbers
A prime number is a whole number greater than 1 that has exactly two factors: 1 and itself.
A composite number is a whole number that has more than two factors.
The number 1 is a special case and is neither prime nor composite because it has only one factor.
Section 2
Identifying Even Composite Numbers
All even numbers greater than 2 are composite numbers. This is because they are divisible by 2, meaning they have 2 as a factor in addition to 1 and the number itself.
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Section 1
Defining Prime and Composite Numbers
A prime number is a whole number greater than 1 that has exactly two factors: 1 and itself.
A composite number is a whole number that has more than two factors.
The number 1 is a special case and is neither prime nor composite because it has only one factor.
Section 2
Identifying Even Composite Numbers
All even numbers greater than 2 are composite numbers. This is because they are divisible by 2, meaning they have 2 as a factor in addition to 1 and the number itself.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter