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.

Activity 1 4 23, Represented

Problem 1

Here is how Clare and Andre represented  .

Clare
Base ten blocks. 8 tens, 12 ones.
Andre
Area diagram representing 4 times 23.
  1. How does each diagram show ?

  2. How could we use Clare’s diagram to find the value of ?

  3. How could we use Andre’s diagram to find the value of ?

Problem 2

Diego tried different ways to partition or split a diagram to help him find the value of .

A
Area diagram. Rectangle divided into 2 parts. One part, top measurement of 12, the other, top measurement of 11. Left side measurement 4.
C
Area diagram. Rectangle divided into 2 parts. One part, top measurement of 10, the other, top measurement of 13. Left side measurement 4.
B
Area diagram. Rectangle divided into 2 parts. One part, top measurement of 15, the other, top measurement of 8. Left side measurement 4.
D
Area diagram. Rectangle divided into 2 parts. One part, top measurement of 20, the other, top measurement of 3. Left side measurement 4.
  1. What do you notice about the numbers in his diagrams?

  2. Which diagram would you use to find the value of ? Explain your reasoning.

Problem 3

Find the value of . Show your thinking using diagrams, symbols, or other representations.

Activity 2 Some Fine Products

Problem 1

To find the value of , Mai started by writing this equation:

Describe or show what Mai would do to finish finding the value of .

Problem 2

Find the value of each product. Show your reasoning.

Activity 3 Play Close to 100, Multiplication

Students playing Close to 100, Multiplication.

Play Close to 100, Multiplication with a partner.

  1. Place the cards face down.

  2. Each player draws 4 cards.

  3. 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.

  4. Player closest to 100 wins.

  5. Play 5 rounds. Player who wins the most rounds wins.

Game 1

Round 1

Round 2

Round 3

Round 4

Round 5

Game 2

Round 1

Round 2

Round 3

Round 4

Round 5

Practice Problem

Problem 1

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