Lesson 9

Workshop: Reasoning from Known Facts

Est. Class Sessions: 2

Daily Practice and Problems

Teacher Notes
X
  1. Possible response: I do not agree with Mara. 1 − 2 is not equal to 1 and 2 + 1 does not equal 1. There are only two number sentences in the fact family for 1, 1, and 2.
  2.  7 = 5 + 2, 7 −  2 = 5, 2 + 5 = 7, 7 − 5 = 2
  3. 1 + 8 = 9, 8 + 1 = 9, 9 − 1 = 8, 9 − 8 = 1

Ongoing Assessment

Use DPP item FF to assess students' fluency with the addition facts [E7] and abilities to determine the unknown number in an addition or subtraction sentence relating three whole numbers for the facts in Groups A–B [E8].

FF. Fact Families

  1. Mara wrote number sentences to show the fact family for 1, 1, and 2.
    1 + 1 = 2           2 − 1 = 1
    2 + 1 = 1           1 − 2 = 1

    Do you agree with her? Why or why not?
  2. Complete the fact family for 2, 5, and 7.
    = 5 + 2           _______________

    7 − = 5           _______________
  3. Show the fact family for 1, 8, and 9.
    _______________           _______________

    _______________           _______________