Learn on PengiEureka Math, Grade 4Chapter 14: Reasoning with Divisibility

Lesson 1: Find factor pairs for numbers to 100, and use understanding of factors to define prime and composite.

This Grade 4 Eureka Math lesson introduces students to finding factor pairs for numbers up to 100 using arrays and area models, then builds on that understanding to define prime and composite numbers. Students practice identifying all factor pairs of a given number by systematically connecting pairs such as 1 and 18, 2 and 9, and 3 and 6, learning to confirm when they have found every pair. The lesson is part of Chapter 14: Reasoning with Divisibility and connects multiplication fluency to foundational number theory concepts.

Section 1

Defining Factors and Factor Pairs

Property

Factors are numbers that are multiplied together to get a product.
If $a \times b = c$ , then $a$ and $b$ are factors of $c$ .
The set $(a, b)$ is called a factor pair of $c$ .

Examples

Section 2

Defining Prime and Composite Numbers

Property

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.

Examples

Lesson overview

Expand to review the lesson summary and core properties.

Expand

Section 1

Defining Factors and Factor Pairs

Property

Factors are numbers that are multiplied together to get a product.
If $a \times b = c$ , then $a$ and $b$ are factors of $c$ .
The set $(a, b)$ is called a factor pair of $c$ .