Previously, students multiplied two factors where one factor was a one-digit number and the other a teen number. The purpose of this activity is for students to make sense of multiplication of a one-digit number and a two-digit number greater than 20. Students analyze representations used to find and articulate reasons for using strategies that are based on the distributive property and place value to find such products (MP7). Along the way, students see that decomposing the two-digit factor into tens and ones is particularly helpful for multiplying. Students also reinforce connections they have made between area diagrams and multiplication expressions.

• “What representations did you use in the last question to show ? How did they help you find the product?” (Base-ten blocks helped me break the 28 into tens and ones. A diagram with a grid helped me break 28 into smaller numbers. A diagram with no grid helped me think about the numbers as I labeled it without worrying about all the little squares.)

The purpose of this activity is for students to continue to multiply single-digit whole numbers and numbers greater than 20. The opening problem encourages students to apply place-value reasoning (decomposing two-digit numbers into tens and ones) and properties of operations to reason numerically about products. Because one of the factors is 2, however, students may use repeated addition (such as ) to find subsequent products. In the Activity Synthesis, emphasize strategies that are based on place value and multiplication, connecting the numerical expressions with diagrams as needed.

• Invite 1–2 students to share their responses and reasoning. Display or record their work for all to see. 
• Discuss responses that highlight use of place value and properties of operations. , for instance, can be found using the associative property ( or distributive property ( ).
• Consider using diagrams or base-ten blocks to reinforce the meaning of expressions as needed.

The purpose of this activity is for students to play a game in which they are able to apply the strategies they’ve learned for multiplying one-digit numbers by two-digit numbers. Students use digits to create an expression that has a value as close to 100 as possible. The first game includes teen numbers, and the second game includes two-digit numbers greater than 20.

This activity is optional because it provides extra practice for multiplying by two-digit factors. Depending on the time available, students can play 1 or 2 games.

• “What were some strategies that were helpful as you played Close to 100?” (I used rounding to think about how large the product would be. I multiplied the tens and ones, then added the results to find the product.)