Lesson 8 Multiply 2 Two-digit Numbers

- Let’s multiply 2 two-digit numbers.

Warm-up Number Talk: Extra Groups

Find the value of each expression mentally.

$20 \times 60$
$21 \times 60$
$20 \times 62$
$19 \times 60$

Activity 1 Two by Two

Problem 1

For each diagram, write a multiplication expression that the diagram can represent. Then, find the value of the expression. Use equations to show or explain your reasoning.

Problem 2

How are the diagrams alike? How are they different? Discuss with your partner.

Problem 3

Use a diagram to find each product.

$13 \times 21$
$25 \times 46$

Activity 2 Decompose by Place Value

Problem 1

These diagrams could be used to find the value of $49 \times 57$ .

Diagram, rectangle partitioned vertically and horizontally into 4 rectangles. — Diagram A

Which diagram is more helpful when finding the value of $49 \times 57$ ? Why?

Problem 2

Use a diagram to find each product.

$49 \times 57$
$29 \times 55$

Practice Problem

Problem 1

Use the diagram to find the value of $47 \times 62$ .
Would this diagram be helpful to find the value of $47 \times 62$ ? Explain your reasoning.