Lesson 2

100 Links

Est. Class Sessions: 1

Developing the Lesson

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A 100-link chain is quite long. If possible, use an open area for this activity.

Make a 100-Link Chain. Assign students to groups of four. Distribute two different-colored sets of 50 links to each group. Have groups sort the links into groups of 10 of the same color and then make a chain of 100 links by alternating colors every 10 links. See Figure 1.

As student groups begin to complete their chains, encourage them to think about how they can check the lengths of their chains by asking questions similar to the following:

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  • How do you know that you have 100 links in your chain? (Possible response: We counted all the links.)
  • How do you know that you counted correctly? How did you count? (Possible response: We counted each group by ones to get ten in each. Then we counted 10 groups.)
  • How can you check your chain? (Possible responses: Count all the links again by ones. Count each group of ten by ones, then count the groups by tens to get to 100.)
  • Is there a quicker way to check each group? (We can check to see if they are the same length.)

If students do not suggest that they compare chains with another group, ask:

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  • How can you work with another group to check to see if your chains have 100 links? (Possible responses: Have the other group count our links. Compare the chains to see if they are the same length.)

Have groups compare chains with one another to ensure that all chains have 100 links.

Compare 100-Link Chain to 100 Chart. In a whole-class discussion, relate the 10 rows on the 100 Chart to the 10 groups of ten in their 100-link chains.

Display and refer students to the 100 Chart from the Student Activity Book Reference section.

Ask:

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  • Describe the pattern you made with your chains. (The chain colors alternate with every ten links. For example, ten reds and ten blues, and then ten reds and ten blues again.)
  • How many groups of ten are in your chain? Let's count. (1, 2, 3…10)
  • How many links are there altogether? (100 links) How can we find out for sure? (Possible response: Count by tens: 10, 20, 30…100 links.)
  • How many numbers are on the 100 Chart? (100)
  • What is the largest number on the 100 Chart? (100)
  • Let's count the number of rows on the 100 Chart.
    (1, 2, 3…10)
  • How many numbers or squares are in each row? (10)
  • There are ten rows of ten numbers on the 100 Chart. How is the 100 Chart like your 100-link chain? (Possible responses: They both stop at 100; the rows are like the groups of ten on the chain; there are ten rows of the chart and ten groups in the chain; there are ten squares in the rows and ten links in the groups.)

Partition 100 into Two Parts. Direct students' attention to the 100-Link Chain page in the Student Activity Book. Ask each group to break their chain into two parts but only where one color stops and the new color starts (they cannot break the chain within a group of ten). Tell students that the two parts do not have to be equal. See Figure 2. Ask groups to count the number of links in each part and write a corresponding number sentence on the 100-Link Chain page in the Student Activity Book.

Students in each group can take turns breaking the chain into two parts and then work together as a group to write a corresponding number sentence. In that way, each group will complete four number sentences. As groups work, check to see that they are dividing the chains into two parts where the colors change and that they put their chains back together again before another student breaks the chain. Tell students that if one student breaks the chain in the same place as another student, they should put the chain back together and break it at another spot.

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To avoid confusion, use the term parts of the chain to refer to the two sections of the chain that students make when they break the chain. Use groups of ten or just tens to refer to each colored section of ten links. For example, ask, "How many groups of ten are in this part of the chain?" or "How many tens are in this part of the chain?"

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Challenge groups that complete the two-part number sentences to break the chain into three parts and write number sentences with three addends. For example:
30 + 60 + 10 = 100.

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Use the 100-Link Chain page in the Student Activity Book to assess students' progress toward representing and partitioning 100 into groups of ten [E2, E1], writing numbers to 100 [E4], writing number sentences for addition situations [E3], and solving addition problems involving multiples of ten using links [E7]. To provide targeted practice with these Expectations, place 100-link chains and copies of the 100-Link Chain page in a learning center.

Share Strategies for Adding Tens. Talk with groups about their strategies for completing the number sentences. Encourage students to skip count by tens to determine the number of links in each part. They can also make connections between the addition facts for ten and multiples of ten to complete the sentences. For example, 8 + 2 = 10, so 8 tens plus 2 tens is 100 tens or 80 + 20 = 100. Calculators can be used to check their number sentences. See the Sample Dialog.

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The following dialog of a teacher

working with two groups is adapted from

classroom videos of students working

on this activity.

Group 1

Teacher: I see that your first number sentence is 40 + 60 = 100. What did you do to figure that out?

John: We counted them. [He points to each group of ten in the first part of the chain.] One, two, three, four.

Teacher: So, you have four groups of ten in the first part. How many links is that?

John: 40.

Teacher: Good. How do you know it is 40 links?

John: I just knew. I did it in my head.

Teacher: What did you do in your head?

John: Umm. I went 1, 2, 3, 4, so 10, 20, 30, 40.

Teacher: Okay, now I understand your thinking. [She turns to the rest of the group.] How many are in the second part?

Jackie: 6.

Teacher: 6 links?

Jackie: No. 6 tens.

Teacher: So 6 tens are how many links?

Jackie: 60.

Teacher: Show me with the links. [Jackie counts each group of colored links by tens to 60.]

Group 2

Teacher: I see that you have already written 100 as the answer for all your number sentences. How did you come up with 100 for all of them?

Irma: Everything would be 100.

Jessie: Yeah. They are all going to equal 100 because there's 100 links all the time.

Teacher: Oh. So what is your number sentence?

Jessie: 30 + 70 = 100.

Luis: [Shows the teacher and the group one part of a chain.] 30. It's official.

Teacher: Luis came up with 30. Okay, I want to know something. [She gathers up the second part of the chain and covers it up.] Without looking at it, how many links do you think are in this part?

Frank: [Holds up ten fingers. He begins counting on, beginning with the fourth finger of one hand and pointing to his remaining fingers.] 40, 50, 60, 70, 80, 90, 100.

Teacher: So how many tens?

Frank: 7.

Teacher: 7 tens or …?

Jessie: 70!

Teacher: Let's check to see if you are right. Who would like to check? Irma, see if there are 70.

Irma: 10, 20, 30, 40, 50. [Irma misses a group of ten. Teacher interjects and they count again to 70.]

Teacher: So what is your number sentence?

Irma: 30 + 70 = 100.

Teacher: Is there another way that you could figure that out?

Luis: Yeah. I knew 3 + 7 = 10, so then it must be
30 + 70.

Teacher: Good thinking. 3 tens plus 7 tens is 10 tens and that is the same as 30 plus 70 equals 100.

Adventure Book:
Student Activity Book: 319
Answers
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SAB_Mini
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Master:
Using groups of 10 links in alternating colors to make a 100-link chain
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Partitioning 100 links into two parts
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