Understanding the Sieve of Eratosthenes

This video tutorial is part of Grade 4, Module 3, Lesson 25, focusing on exploring the properties of prime and composite numbers up to 100 using multiples. The lesson includes a homework problem where students use the sieve method to identify all prime numbers less than 100. The video provides a step-by-step guide to completing this task, highlighting the process of marking and shading numbers to distinguish between prime and composite numbers. The tutorial concludes with an analysis of the results, emphasizing the identification of prime and composite numbers.

What is the main objective of this lesson?

• To learn addition and subtraction

• To explore properties of prime and composite numbers

• To study fractions and decimals

• To understand geometry basics

Which method is used in the homework problem to find prime numbers?

• Long division

• Sieve of Eratosthenes

• Multiplication table

• Factorization

What is the first step in the Sieve of Eratosthenes?

• List all numbers up to 100

• Cross out all even numbers

• Circle the number two

• Shade the number one red

Which number is shaded red in the Sieve of Eratosthenes?

• 5

• 3

• 2

• 1

What is the significance of the number one in the Sieve of Eratosthenes?

• It is a prime number

• It is the largest number

• It is a composite number

• It is neither prime nor composite

After shading the number one red, what is the next step?

• Cross out all multiples of two

• Circle the first unmarked number

• Shade all prime numbers

• List all composite numbers

What should you do after circling the first unmarked number?

• Write it down separately

• Cross out every multiple of that number

• Shade it blue

• Erase it

Why do we cross out multiples of a number in the Sieve of Eratosthenes?

• To eliminate composite numbers

• To identify even numbers

• To find odd numbers

• To highlight prime numbers

What is the purpose of repeating steps two and three?

• To identify all odd numbers

• To ensure all numbers are shaded

• To find all prime numbers

• To list all even numbers

What color should the crossed-out numbers be shaded?

• Orange

• Yellow

• Blue

• Green