Multi-Digit Multiplication

Unit Review Sheet

Facts and Definitions

Lesson 1: Back to Multiplication Basics

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Lesson 2: Multiples of 10, 100, and 1000

• Multiplication can be thought of as the addition of equal groups. For example, 2×10 means 2 groups of 10 added together.

Lesson 3: Multiples of 10, 100, and Beyond!

• When you multiply by a multiple of 10, as a shortcut, you can multiply the two non-zero numbers together and then add together the number of zeros from each factor. For example, for 20×400, you'd multiply 2×4 (8) and then add the total number of zeros (one from 20 + two from 400 = three) to the end (800)

Lesson 4: Multi-Digit Multiplication Using Arrays

• One method for solving multiplication problems is to use arrays to split a problem into more easily manageable chunks. For example, for the problem 23×3, you can split 23 into 10+10+3 and then draw two arrays that show 10×3 and one array that shows 3×3. Those arrays make it easier to see 30+30+9=69.
• A base-10 array is a method of solving multiplication problems using images of base-10 blocks.

Lesson 5: The Area Model

• An area model is a rectangular diagram of a multiplication problem. In an area model, the two factors are shown as the length and width of the rectangle. Each factor is broken into more manageable chunks (and the rectangle into smaller rectangles). You find the area of each of the smaller rectangles (partial products) and then add them together to get the total area of the rectangle (the whole product).

Lesson 6: The Standard Multiplication Algorithm

• algorithm: a set of steps that can be used to solve a particular type of problem
• The standard algorithm for multiplication is a common approach to solving multiplication problems where factors are stacked vertically and a series of steps are followed to find the product
• When using the standard algorithm for multiplication, it is important to line up the places of the two factors correctly (for example, the ones place of the first factor directly on top of the ones place of the second factor)

Lesson 7: Multiplication Practice

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Lesson 8: Unit Test

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Final Project: Multiplication Contract

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