Decimals Practice exchanging (after lesson 8)

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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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