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How to Teach the Connections Between Addition and Subtraction

You can show the connections between addition and subtraction by teaching your kindergarten students related numbers called fact families (e.g. 2, 3, and 5). For addition the two smallest numbers in a fact family can be added together to make the largest number. The order of the two smallest numbers can be reversed and the addition problem will have the same sum. For subtraction you can subtract one of the small numbers in the fact family from the largest number and the difference will be the other small number (e.g. 5-2=3). The order of the two smallest numbers in the subtraction problem can also be reversed and have an answer in the same fact family (e.g. 5-2=3 and 5-3=2). To teach each fact family you can make a "fact family house" using a pocket chart (a rectangular shaped chart with clear pockets) to hold the number and math symbol cards. The chart can be found at most teacher supply stores.

Things You'll Need

  • Construction paper
  • Scissors
  • Marker
  • Fact family pocket chart
  • 4 pocket chart number cards for each number 1-10
  • 4 pocket chart math symbol cards for each math symbol
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Instructions

    • 1

      Make four "fact family houses" for the pocket chart. Cut out large triangles from sheets of construction paper that will fit in the top pocket of the pocket chart that will be the 'roof' for each fact family house. Write a fact family on each of the construction paper roofs using a marker (e.g. 1, 2 and 3; 2, 3, and 5; 3, 4 and 7; 4, 5 and 9). Fold two sheets of construction paper in half horizontally and cut out the rectangles with your scissors. Laminate cut out shapes for each fact family house.

    • 2

      Place the first fact family triangle for the roof in the top row or pocket of the pocket chart. Place each of the four rectangles in the next four pockets beneath the roof to complete the fact family house. Say the three numbers for the first fact family as you point to each of them. Tell your students that these three numbers are a family and are related because they can be used to make two addition number sentences and two subtraction number sentences.

    • 3

      Place an addition symbol and an equal symbol in each of the next two rows or pockets of the pocket chart, leaving room to add the number cards. Tell your students that to make the correct addition number sentence the largest number must go last. Place the largest number behind the equal sign in the first row then add the other two numbers in the number sentence on each side of the addition symbol (e.g. 3+2=5). Tell your students changing the order of the two smallest numbers will also make another correct addition number sentence and place the numbers and symbols on the second row changing the first two numbers (e.g. 2+3=5).

    • 4

      Place a subtraction symbol and an equal symbol in each of the next two rows leaving room to add the number cards. Tell your students that to make the correct subtraction number sentence the largest number must go first. Place the largest number in front of the subtraction sign in the third row then add the other two numbers in the number sentence; one behind the subtraction symbol and one behind the equal sign (e.g. 5-2=3). Tell your students changing the order of the two smallest numbers will also make another correct subtraction number sentence and place the numbers and symbols on the second row changing the last two numbers around (e.g. 5-3=2).

    • 5

      Take the numbers off the pocket chart leaving the math symbols (e.g. + or - and =). Invite students to come up and make addition number sentences using the fact family cards. Remind them that the biggest number should go last in an addition number sentence if they need a reminder. Invite students to come up and make subtraction number sentences. Remind them that the biggest number should go first in subtraction number sentences if they need a reminder. Change the fact family 'roof' of the house and the number cards to let students make new fact families number sentences.

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