Section 1
Identifying Even Composite Numbers
Property
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.
In this Grade 4 Eureka Math lesson from Chapter 14, students explore the properties of prime and composite numbers up to 100 by using the Sieve of Eratosthenes to systematically cross out multiples and identify which numbers remain. Students practice distinguishing between factors and multiples, recognize that multiples are infinite while factors are finite, and determine whether numbers are prime or composite based on their factor pairs. By the end of the lesson, students can identify all prime and composite numbers to 100 and explain why certain numbers, like 1, fit neither category.
Section 1
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.
Section 2
Finding Prime Numbers Using the Sieve of Eratosthenes
The Sieve of Eratosthenes is an algorithm for finding all prime numbers up to a specified limit. It works by creating a list of integers and systematically eliminating composite numbers by crossing out the multiples of each prime, starting with the first prime number, 2. The numbers that are not crossed out are the prime numbers.
Expand to review the lesson summary and core properties.
Section 1
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.
Section 2
Finding Prime Numbers Using the Sieve of Eratosthenes
The Sieve of Eratosthenes is an algorithm for finding all prime numbers up to a specified limit. It works by creating a list of integers and systematically eliminating composite numbers by crossing out the multiples of each prime, starting with the first prime number, 2. The numbers that are not crossed out are the prime numbers.