Lesson 4

Hundredths

Est. Class Sessions: 2–4

Developing the Lesson

Part 2. Using a Hundredths Chart

Complete the Chart. Refer students to the Using a Hundredths Chart pages in the Student Activity Book. Display the Hundredths Chart and ask students to skip count by hundredths starting at one-hundredth and going to ten-hundredths. Note that ten-hundredths and one-tenth are equivalent when filling in the missing numbers.

Ask:

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  • Where on the chart is one-hundredth? (top-left corner)
  • What base-ten piece shows one-hundredth if a flat is one whole? (a bit)
  • What base-ten pieces show ten-hundredths? (ten bits or one skinny)
  • How can you explain to someone who is not in the class that one-tenth and ten-hundredths are equal? What tools would you use? (Students can use base-ten pieces, the Hundredths Chart, money, or a meterstick.)
  • Which base-ten piece shows one-tenth if a flat is one-whole? (a skinny)
  • What number is in the lower right corner? (one whole)
  • What base-ten piece shows one whole? (a flat)
  • What is another way to write one whole using decimal fractions? (1.0 or 1.00)

Have students complete the Hundredths Chart on their own, comparing their work with a partner.

Patterns on the Hundredths Chart. Have pairs complete Questions 1 and 2 on the Using a Hundreths Chart pages in the Student Activity Book. Then have them describe their patterns from Question 2 to the class using the displayed Hundredths Chart. Encourage the class to ask presenters clarifying questions. Facilitate the conversation by asking questions that will connect the patterns to the numbers. You can display a 100 Chart for comparison. See the sample dialog.

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Discuss patterns on the Hundredths Chart.

Teacher: What patterns did you notice?

Keenya: The first row has zeros after the decimal point.

Teacher: Good observation. Use what you know about place value to tell us why that is true.

Keenya: Because the numbers in the first row are like bits. They are just hundredths. There aren't any tenths.

Teacher: So what do the zeros after the decimal tell you?

Keenya: They mean there are no tenths in those numbers.

Luis: The Hundredths Chart looks like the 100 Charts we used in second grade.

Teacher: They do. How are they alike and different?

Luis: The numbers are mostly the same, but there aren't any decimal points in the 100 Chart.

Teacher: Okay, and what if we look at the numbers in the last column. Do you see any patterns there?

Luis: I do. They all only have one digit after the decimal.

Teacher: What are the numbers? Skip count down the last column.

Luis: one-tenth, two-tenths, three-tenths… nine-tenths, one.

Teacher: Who can explain how the numbers in the last column are like the numbers in the last column of the 100 Chart? Talk it over with your partner. [Teacher displays a 100 Chart.]

Lee Yah: The numbers in the 100 Chart are the tens and the numbers in the Hundredths Chart are the tenths.

Teacher: Right. Is there another way to write the numbers in the tenths column so they look more like the tens in the 100 Chart?

Grace: You can write them with a zero after them. Like 0.10 and 0.20.

Teacher: Use what you know about place value to tell me why 0.1 and 0.10 are equal.

Grace: The zero in the hundredths place tells there are no hundredths, just one tenth.

Adding and Subtracting 0.01 and 0.1. Have students complete Questions 3–8 on the Using a Hundredths Chart pages in the Student Activity Book on their own so they develop their own strategies for adding and subtracting 0.01 and 0.1 using the Hundredths Chart.

As students work, ask:

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  • How can you use the chart to show what number is 0.01 more than 0.75? (Move one box to the right on the chart to 0.76.)
  • How can you use the chart to show what number is 0.01 less than 0.75? (Move one box to the left on the chart to 0.74.)
  • How can you use the chart to show what number is 0.1 more than 0.75? (Since 0.1 is the same as 0.10 (ten hundredths), use the chart to count on by hundredths ten times: Start at 0.75, then count 0.76, 0.77 … 0.85.)
  • Where did you land? (One row after 0.75 on the chart.)
  • Knowing that 0.1 is the same as ten-hundredths, how can you use the chart to subtract 0.1? (Move to the row before 0.75 on the chart.)

Have students discuss strategies for moving on the chart. In particular, discuss what happens at the beginning and end of the rows as in Questions 7 and 8.

Assign the Many Ways to Show Hundredths page in the Student Activity Book for homework.

Student Guide:
Student Activity Book: 421 423
Answers
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SG_Mini
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Master: