## Lesson: Modeling and Recording SubtractionIntroducing the Concept

Children first learn the concept of subtraction by subtracting 1 from the numbers 1 to 10. At the Kindergarten level they will model subtraction by counting back and recording the number of items remaining.

Materials: overhead projector, counters, number cards for the numbers 0–10, and the minus sign and equals sign (Learning Tools 8 and 9 in the Learning Tools Folder)

Preparation: Prepare cards for numbers 0–10 and the minus and equals symbols.

Prerequisite Skills and Concepts: Children should be proficient in counting and recognizing numbers to 10. Children should have experience finding sums to 10.

• Say: I would like volunteers to help me act out a story.
Have five children come up to the front of the classroom.
• Ask: How many children are at the front of the room?
Children should say “5.”
• Say: Five people are at the front of the room.
Ask one child to sit down.
• Say: Now one less child is at the front of the room. Let's count how many children are left at the front of the room.
Have children count aloud to 4.
• Ask: What did we do when we asked one person to sit down? (We decreased the group by one.)
Continue subtracting one more child and counting the new number until no children remain at the front of the room.
• Ask: What did we do each time?
Children should say that they took away one from the group.
• Ask: What happened to the number of children each time we subtracted one from the group? (The group had one less each time.)
• Say: Now let's do this with counters.
Place 5 counters on the overhead projector. Direct children to look at the overhead projection.
• Ask: How many counters are there?
Children should say “5.” Place the 5 number card where children can see it. Remove one counter from the overhead.
• Ask: If I take away one counter, how many counters are left? (4)
Place the 4 number card to the left of the 5 card. Repeat, subtracting one until you have placed the number cards for 0 to 5 in a line.
• Ask: Do you see a pattern?
Children should see that when you subtract 1, you count back 1.
• Say: So subtracting one is like counting back one.
Place the cards for 6 to 10 in the line with the others.
• Ask: If I subtract 1 from 10, how many will I have left?
Children should say “9.”
• Say: Ten minus one equals nine.
Point to the appropriate number cards as you say this.
Continue using the number cards to subtract 1 from numbers up to 10. Check the results, using counters on the overhead.
• Say: Now let's learn how to write subtraction sentences.
Put six counters up on the overhead.
• Ask: How many counters do I have?
Children should say “6.” Write 6 on the overhead.
• Say: Now let's subtract one.
Remove one counter and write 1 on the overhead.
• Ask: How many counters are left?
Children should say “5.” Write 5 on the overhead.
• Say: We can show how we subtracted 1 from 6 and got 5 by using math symbols.
Write a minus sign between the 6 and the 1.
• Say: This is a minus sign. It tells us that we are subtracting.
Have children follow you as you model making a minus sign with your finger.
• Ask: Think about how you write an addition sentence. What sign goes here to show that the amounts on either side are the same?
Point to the space between the 1 and the 5. Children should say, “the equals sign.”
• Say: That's right. The equals sign tells us that the amounts on either side are the same.
Continue as above, modeling different subtraction sentences with counters and recording them on the overhead. You may wish to have students volunteer to hold the number cards and the symbol cards that represent what you are subtracting on the overhead.