Fluently Subtracting within 1000

  • Third Grade
  • Math
  • 90 minutes
  • Standards: 3.NBT.A.2
  • no ratings yet
August 17, 2015
by Josephine Alston

Start your students on subtracting three-digit numbers with this lesson that breaks the problems down by place values!

Learning Objectives

Students will be able to solve subtraction problems within 1,000.

Download Lesson Plan

Lesson

Introduction (15 minutes)

  • Invite students to bring their math journals and a pencil to the class meeting area.
  • Tell them to place their supplies on the floor next to them.
  • Tell the students that today we're going to learn a strategy for solving subtraction problems within 1,000.
  • Let the students know that to solve for these problems they must have a strong grasp of place value, which we will do a review of, before proceeding.
  • On the board write “Place Value.” Under this term, write the following:
    Place: The position of a digit in a number.     
    10,000s      1,000s      100s      10s      1s 
    Value: The value of the digit in its place
  • Ask students what the term place means in regards to a number. As the students share, place the correct definition next to the term.
  • Then, ask the students to share what the term value means in regards to a number. As the students share, place the correct definition next to the term.
  • Next, come up with a number, for example 14,262, to show the students how to correlate or determine the place and value of specific digits. Make a chart on the board showing these values. For example:
                   1             4           2          6        2 
    Place:       10,000s       1,000s       100s       10s       1s           
    Value:       10,000        4,000        200        60        2
                (10,000x1)    (1000x4)     (100x2)    (10x6)    (1x2)

Explicit Instruction/Teacher Modeling (15 minutes)

  • Direct the students’ attention to the board.
  • Write a few subtraction problems, within 1,000, on the board, such as 887-498 or 978-683.
  • Tell the students that the first thing we want to do is rewrite the problem in place value format, as follows: (800 + 80 + 7) - (400 + 90 + 8).
  • Next, tell the students that we will add the numbers, on both sides of the equal sign, based on place value, as follows: (800 - 400) + (80-90) + (7-8).
  • With student input, continue to solve the above problem until you find the answer of 389.

Guided Practice/Interactive Modeling (15 minutes)

  • Tell the students to pick up their supplies and write down and solve the other problem, 978 - 683, using what’s been termed the "Place Value Method for Subtraction," on the board.
  • Ask for volunteers to raise their hands and share with the class the steps involved based on the problem just completed.
  • Give the students time to solve the problem.
  • As the problem is being solved aloud by the class, write down the steps volunteered by the students on the whiteboard.
  • When the problem is done, review it with the class for accuracy. Make sure everyone has the problem written down as a reference for completing their assignment during independent work time.

Independent Working Time (20 minutes)

  • Send the students back to their seats.
  • Pass out the Subtraction Math worksheets.
  • Walk around and observe the students as they work on completing the assignment.
  • Monitor the students as they work, making sure the problems are done correctly, in that they are justifying their answers by showing their work.
  • During this time, the teacher will ask questions of the students to make sure they understand the concept of subtracting within 1,000 using place value.
  • The teacher will also answer questions by the students, to help them clarify any misconceptions they may have.

Extend

Differentiation

  • Enrichment: Students can be given an additional worksheet if they finish early, additionally, students may start practicing subtracting four-digit numbers.
  • Support: Observe and monitor these students more closely. Get involved in helping the students solve the problems. These students would also benefit from the use of manipulatives.

Technology Integration

Related Books and/or Media

Review

Assessment (10 minutes)

  • The students will be assessed based on the comments and feedback from them during the lesson about the assignment and at the conclusion of the lesson.
  • They will also be assessed based on the results of the completed problems assigned.

Review and Closing (15 minutes)

  • Bring the students back to the class meeting area.
  • Ask for volunteers to share their answers and work for the problems assigned.
  • As the problems are reviewed in front of the class, the students will check their answers for accuracy.
  • After each problem has been checked for accuracy, ask the class if there are any questions or comments on solving for subtraction problems within 1,000 using place value.

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