Say: I am planning a party for this weekend. I will have 10 guests. I need to buy party favors for my guests. I know that 4 of them are girls. I need to know how many boys to buy party favors for. Can you figure out how many boys will be at my party? Turn to your neighbor and talk about the question.
Say: Today we are going to solve some problems using something called part-part-whole. Part-part-whole is the same thing as addition and subtraction. We are going to use a tool called a number bond to help us solve our problems.
1. Show the number bond (attached) on the interactive whiteboard or draw one on the board or on chart paper. Show students that the circle that is by itself is where we put the whole number. The other two circles are the parts, or addends. Tell them that addends are numbers that are being added in an addition sentence.
2. Think about the problem we talked about earlier. What number do you think I would put in the top circle? What number is the whole number? Do you agree or disagree with that answer? Why? (Students should come to the conclusion that 10 will be in the top circle)
3. What did I know from the problem? (Pause for student answers) We knew that I had 10 total guests and 4 of them were girls. Where do you think we should put the 4? (Allow student responses to determine the 4 should go in one of the part circles)
4. Have a student add four counters to the interactive whiteboard display (if you are not using a board, you can use a piece of chart paper to draw your number bond and place the counters).
5. Look at our number bond. What are we missing? (Allow student responses)
6. What are some ways that we could find that missing part? Students should share strategies such as counting on, using subtraction, relate the problem to addition facts, etc. Have a student count on using cubes to fill in the missing part on the number bond. Ask: How could we write this as a number sentence? What would our number sentence look like? Does it matter in what order you write your number sentence? Can it be written like this 10=4 +6? Why?
7. Have students work with a partner. Tell them they are going to work together to solve some word problems. Give each pair a number bond (attached) and some counters. Each pair will also receive a set of task cards with missing addend word problems.
8. Have the students use the number bond and counters to solve the problems on their task cards (students can use other strategies if they do not need the manipulatives). Tell students to circle the number that was missing after they complete their number sentence.
9. After students have completed the task cards, have everyone come to the carpet and lay out their cards. Compare and contrast the cards and have students share how they solved the problems.