Lesson 16 Multiply Numbers Larger than 20

- Let’s multiply numbers that are larger than 20.

Warm-up Number Talk: Three Times Some Numbers

Find the value of each expression mentally.

$3 \times 10$
$3 \times 20$
$3 \times 50$
$3 \times 25$

Activity 1 4 $\times$ 23, Represented

Problem 1

Here is how Clare and Andre represented $4 \times 23$ .

Base ten blocks. 8 tens, 12 ones. — Clare

Area diagram representing 4 times 23. — Andre

How does each diagram show $4 \times 23$ ?
How could we use Clare’s diagram to find the value of $4 \times 23$ ?
How could we use Andre’s diagram to find the value of $4 \times 23$ ?

Problem 2

Diego tried different ways to partition or split a diagram to help him find the value of $4 \times 23$ .

Area diagram. Rectangle divided into 2 parts. One part, top measurement of 12, the other, top measurement of 11. Left side measurement 4. — A

Area diagram. Rectangle divided into 2 parts. One part, top measurement of 10, the other, top measurement of 13. Left side measurement 4. — C

Area diagram. Rectangle divided into 2 parts. One part, top measurement of 15, the other, top measurement of 8. Left side measurement 4. — B

Area diagram. Rectangle divided into 2 parts. One part, top measurement of 20, the other, top measurement of 3. Left side measurement 4. — D

What do you notice about the numbers in his diagrams?
Which diagram would you use to find the value of $4 \times 23$ ? Explain your reasoning.

Problem 3

Find the value of $3 \times 28$ . Show your thinking using diagrams, symbols, or other representations.

Activity 2 Some Fine Products

Problem 1

To find the value of $2 \times 37$ , Mai started by writing this equation:

$2 \times 30 = 60$

Describe or show what Mai would do to finish finding the value of $2 \times 37$ .

Problem 2

Find the value of each product. Show your reasoning.

$3 \times 32$
$2 \times 43$
$4 \times 22$
$3 \times 29$

Activity 3 Play Close to 100, Multiplication

Students playing Close to 100, Multiplication.

Play Close to 100, Multiplication with a partner.

Place the cards face down.
Each player draws 4 cards.
Each player chooses 2 cards to complete the expression to make a value as close to 100 as possible. Write the 2 digits and the product.
Player closest to 100 wins.
Play 5 rounds. Player who wins the most rounds wins.

Game 1

Round 1

$\times 1 =$

Round 2

$\times 1 =$

Round 3

$\times 1 =$

Round 4

$\times 1 =$

Round 5

$\times 1 =$

Game 2

Round 1

$\times 2 =$

Round 2

$\times 2 =$

Round 3

$\times 2 =$

Round 4

$\times 2 =$

Round 5

$\times 2 =$

Practice Problem

Problem 1

Find the value of each expression. Explain or show your reasoning.

$2 \times 47$
$3 \times 25$

Lesson 16 Multiply Numbers Larger than 20

Warm-up Number Talk: Three Times Some Numbers

Activity 1 4 × 23, Represented

Problem 1

Problem 2

Problem 3

Activity 2 Some Fine Products

Problem 1

Problem 2

Activity 3 Play Close to 100, Multiplication

Practice Problem

Problem 1

Activity 1 4 $\times$ 23, Represented