Unit 2 Exploring Addition and Subtraction within 20

In Unit 2 students will:

  • Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings and equations with a symbol for the unknown number to represent the problem.
  •  Apply properties of operations as strategies to add and subtract (e.g. 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.)
  • Add and subtract within 20, demonstrating fluency for addition and subtraction within 10.  Use strategies such as counting on; making ten (e.g., 13-4=13-3-1=20-1=9); using the relationship between addition and subtraction (e.g.., knowing that 8+4=12, one knows 12-8=4); and creating equivalent but easier or known sums (e.g., adding 6+7 by creating the known equivalent 6+6+1=12+1=13.).
  • 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.

 By the end of Unit 2 your child should be able to answer the following question:

  • 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?
  • What patterns do I use when I count and connect a written numeral to a set of objects?
  • How does understanding the equal sign help me to balance an equation?

The following videos will support some of the topics covered in Unit 2.

 Add and Subtract within 20

  • Adding Using a Numberline

  • Adding by Making Tens

  • Making Ten- Mental Math Strategy

  • Fact Families

  • Comparison Word Problems

  • Addition Word Problems