Lesson 14

The purpose of this True or False is to elicit strategies students have for determining whether two expressions have the same value. Students may find the value of each expression, or they may reason about the numbers on each side of the equal sign. This will also be helpful later when students compare addition expressions.

• Display one statement.
• “Give me a signal when you know whether the statement is true and can explain how you know.”
• 1 minute: quiet think time

• Share and record answers and strategy.
• Repeat with each equation.

• “Who can restate _____'s reasoning in a different way?”
• “How could you figure out that \(5 + 1\) is not equal to \(5 + 2\) without finding the sum of both sides?” (Both sides have 5 + 1 but the right side has 1 more added on to make \(5 + 2\).)

The purpose of this activity is for students to learn stage 2 of the Number Puzzles center. Students work together to use digit cards to make addition and subtraction equations within 20 true. Each digit card may only be used one time on a page.

• Each group of 2 needs one set of Number Puzzle Digit Cards from stage 1 of this center.

• Groups of 2
• Give each group a set of digit cards and gameboards.
• “We are going to do new Number Puzzles. This time the puzzles are within 20 instead of 10. You need to place the digit cards to make each equation true. Remember, you can only use each digit card once on the gameboard.”

• 10 minutes: center work time

• Display Puzzle 1.
• “Which equation would you start with? Why would you start there?”

The purpose of this activity is for students to choose from activities that focus on adding and subtracting within 20. Students choose from any stage of previously introduced centers.

• Number Puzzles
• Shake and Spill
• Compare

• Gather materials from previous centers:
  • Number Puzzles, Stages 1 and 2
  • Shake and Spill, Stages 3-5
  • Compare, Stage 1

• Groups of 2
• “Now you will choose from centers we have already learned.”
• Display the center choices in the student book.
• “Think about what you would like to do first.”
• 30 seconds: quiet think time

• Invite students to work at the center of their choice.
• 10 minutes: center work time
• “Choose what you would like to do next.”
• 10 minutes: center work time

• “What method do you use most often to add within 20? Why do you use that method the most?”