Unit 4 Exploring Addition and Subtraction within 100

In Unit 4 students will:

  •  Apply properties of operations as strategies to add and subtract.  Examples: If 8+3=11 is known, then 3+8=11 is also known (Commutative Property of Addition). To add 2+6+4, the second two numbers can be added to make a ten, so 2+6+4=2+10=12 (Associative Property of Addition).
  •  Understanding the meaning of the equal sign, and determine if equations involving addition and subtraction are true or false.  For example, which of the following equations are true and which are false? 6=6,7=8-1, 5+2=2+5, 4+1=5+2.
  •  Count to 120, starting at any number less than 120.  In this range, read and write numerals and represent a number of objects with a written numeral.
  •  Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.  Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
  •  Understand that the two digits of a two-digit number represent amounts of tens and ones.  Understand the following as special cases:
    • a. 10 can be thought of as a bundle of ten ones—called a "ten."
    • b. The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones.
    • c. The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six, seven, eight, or nine tens (and 0 ones).
  •  Subtract multiples of 10 in the range 10-90 from multiples of 10 in the range 10-90 (positive or zero differences), using concrete models or drawings and strategies based on place value, properties of operations, and/or relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

 By the end of Unit 4 your child should be able to answer the following questions:

  •  How can I use the context of a story problem to write an equation that solves that problem?
  • How can I use addition and subtraction strategies I've been taught to solve different equations?
  • How do addition and subtraction strategies help me to become more fluent with number facts?
  • How does understanding the equal sign help me to balance an equation?
  • How can I prove that an answer is true?

The following videos explain some of the  topics covered in Unit 4.

 

  • Addition Vocabulary and Commutative Property

  • Making Ten Song

  • Making Ten With 3 Addends

  • Communtative Property

  • Associative Property

 

  • To practice your addition and subtraction skills    (select grade 1 and choose a skill you would like to work on)