Overview
This lecture explains how to use fact families to solve multiplication and division problems, showing how numbers in a family are connected by these operations.
What is a Fact Family?
- A fact family is a set of related multiplication and division equations that use the same three numbers.
- Fact families can be visualized as triangles connecting the three related numbers.
Using Fact Families for Multiplication
- To find a missing product, use the two smaller numbers to get the largest (e.g., 5 × 4 = 20).
- The order of multiplication does not matter (e.g., 4 × 5 = 20).
Using Fact Families for Division
- Division equations use the largest number divided by one of the smaller numbers to get the other (e.g., 20 ÷ 5 = 4).
- Reversing the small number and divisor gives the other division fact (e.g., 20 ÷ 4 = 5).
Practice Examples
- Fact family with 6, 7, and 42: 6 × 7 = 42, 7 × 6 = 42, 42 ÷ 6 = 7, 42 ÷ 7 = 6.
- Fact family with 8, 9, and 72: 8 × 9 = 72, 9 × 8 = 72, 72 ÷ 8 = 9, 72 ÷ 9 = 8.
- Fact family with 5, 7, and 35: 5 × 7 = 35, 7 × 5 = 35, 35 ÷ 5 = 7, 35 ÷ 7 = 5.
Key Terms & Definitions
- Fact Family — A group of related math facts using the same three numbers.
- Product — The result of multiplying two numbers.
- Dividend — The number being divided in a division equation.
- Divisor — The number by which the dividend is divided.
- Quotient — The result of a division problem.
Action Items / Next Steps
- Practice building fact families for other groups of three numbers.
- Be ready to identify or write all four equations for a given fact family.