Unit 4, Lesson 3
Partial Products in Algorithms
Grade 5
Preparation
Lesson Narrative
In previous lessons, students multiplied three-digit numbers by two-digit numbers, using strategies based on place value and the properties of operations. Students used diagrams to illustrate and explain their partial-products calculations.
In this lesson, students move from diagrams to an algorithm that records partial products, which they used in an earlier course when multiplying a two-digit number by a two-digit number. Students relate partial-product expressions to diagrams and then analyze a systematic way to record partial products. This work sets up students to learn the standard algorithm in the next lesson.
- Action and Expression
- MLR8
- Interpret (orally and in writing) different ways to record partial products for a three-digit number multiplied by a two-digit number.
- Match expressions with diagrams to show how partial products can be used to multiply a three-digit number by a two-digit number.
- Let’s find partial products.
Required Preparation
- Create a set of cards from the blackline master for each group of 2.
Teacher Reflection Questions
In a future lesson, students will learn how to use the standard algorithm for multiplication to multiply multi-digit numbers. How do the diagrams and the expressions used in today’s lesson support this work?