Lesson Plan:

Whose is Longer?: Decimals in Expanded Form

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October 6, 2015
by Krystal Douglas

Learning Objectives

Students will be able to write decimals in expanded form.


Introduction (15 minutes)

  • Write "523.912" on the board.
  • Have students read the decimal out loud in proper form (five hundred twenty-three and nine hundred twelve thousandths).
  • Give students tips on saying it properly and correct any misconceptions about pronunciation.
  • Repeat if needed.
  • Pose this question: What is the place value of the digit 3?
  • Have students discuss in their pairs or groups. Encourage them to think deeply about the question.
  • Have a few students share their ideas, and discuss the question as a whole group.
  • Explain that the value is one and the digit tells us there are three of them.

Explicit Instruction/Teacher Modeling (20 minutes)

  • Write "489.215" on the board.
  • Have students copy it down on their whiteboards and read the number to their partner.
  • Encourage students to coach each other.
  • Pose this question: What is the place value of the digit 9?
  • Have students discuss with their groups.
  • Encourage students to explain their reasoning.
  • Explain how the place value of the 9 is ones so we have 9 ones.
  • Ask students to write an equation to explain this.
  • Scaffold their understanding to get to the point where they understand that the expression of the value of the 9 in the ones place is (9 x 1).
  • Pose this question: What is the place value of the 8 and how would we express that in an equation?
  • Have students discuss with their partners.
  • Discuss as a whole group and write the equation on the board (8 x 10).
  • Repeat with the the other digits until you have (4 x 100) (8 x 10) (9 x 1) (2 x 0.1) (1 x 0.01) (5 x 0.001) on the board.
  • Ask students how all of these equations equate to the original number of 489.215.
  • Discuss as a whole group.
  • Lead students to the understanding that each equation represents a digit and the place value of the original number.
  • Explain that students will use this information to play a game.

Guided Practice/Interactive Modeling (30 minutes)

  • Have students get into pairs and cut out the decimal cards.
  • Have them mix the cards up and place them in a pile.
  • Instruct the students to each take a card and not let the other person see it.
  • Have them write their numbers in expanded decimal form following the example that is still on the board.
  • When both partners are done, have them count to three and flip their boards over, showing their decimal in expanded decimal form to their partner.
  • The partner who has the most expressions (most digits) wins that card.
  • The player with the most cards when the game is over is the winner.

Independent Working Time (10 minutes)

  • Distribute the Decimals in Expanded Form worksheet and have students complete it independently.



  • Enrichment Have advanced students also compare the decimals to see which one has the largest decimal.
  • Support Have students who need support play the game using a place value chart so they can recall the value of each place.


Assessment (10 minutes)

  • Collect the worksheets and separate students into groups who need further assistance.
  • Look for students who are not putting the addition sign in between terms and put them into a group.
  • Look for students who are not multiplying the digits by the appropriate place values and put them into a group.
  • Pull these groups aside during the next day's activities to clear up any misconceptions.

Review and Closing (5 minutes)

  • Have students each write on a sticky note one thing they felt successful with and one thing they struggled with today.

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