Decimals Practice exchanging (after lesson 8)

Age

9-12

Materials

• Decimal beads and disks
• Decimal Board
• Paper and pencil

Preparation

Students should have had the Decimal Lessons 1-8 (We are moving from the concrete toward the abstract).

Presentation

Progressive Counting

• 1. Remind students of instances in the past when they have done progressive counting- with bead chains, games involving multiples, and so on.

"The only difference is that we will be doing progressive counting with decimal numbers."

• 2. Select the 0.03 decimal card and have the students write the number as it is in their notebooks and then write 0.36. 0.03------>0.36

Say, "This means that we are going to count by three hundredths until we get to thirty-six hundredths." (like skip counting)

• 3. Have the students lay out three red disks and place them in the hundredth column. The students will then write 0.03 in their Math journals.
• 4. Direct the students to lay out three more hundredth disks to the board, and write the new total (0.06) underneath 0.03 in Math journal.
• 5. Students will continue adding three hundredth disks, exchanging when necessary and recording the new amounts until they have reached 0.36.

0.03 -->0.36 = 0.33 0.30 0.27 0.24 0.21 0.18 0.15 0.12 0.09 0.06 0.03

• 6. Provide practice problems and eventually let the students plan their own set.

EXTENSION: Regressive Counting Invite the students to practice counting backwards from some decimal number to a lower one. for instance: 0.50 ---->0.05 or 0.36 ---> 0.03

Control Of Error

Teacher guided.

Points Of Interest

Participating with the new knowledge helps move the concrete experiences toward abstract thinking

Purpose

• To make a visual, auditory and kinesthetic impression upon the child on how whole numbers are divided into smaller units-decimals.

Variation

Students can practice these problems with or without materials and record them in their Math journals:

PROGRESSIVE COUNTING: 0.4 --> 2.0 0.02 --> 0.12 0.0005 ---> 0.050 0.02 ---> 0.022 4.04 ---> 60.60 0.08 ---> 0.72 0.0006 ---> 0.0162 0.24 ---> 2.40 0.13 ---> 1.30 33.33 ---> 333.30 7.07 ---> 106.05 Plan your own set

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