Kindergarten Mathematics
Unit 3
Counting, Cardinality, and Algebraic Thinking

Printable Parent Letter

During Unit 3, your children will use numbers to 20, including written numerals, to represent quantities and to solve quantitative problems, such as counting objects in a set; counting out a given number of objects; comparing sets or numerals; and modeling simple joining and separating situations with sets of objects, or eventually with equations such as 5 + 2 = 7 and 7 – 2 = 5.   Students will develop the understanding of groups of ten and leftover ones to form numbers up to 20.

Students need to:

  • Review counting to 100 by ones and tens
  • Review counting forward from a number other than 1
  • Write the numbers 0-20 and represent an amount of object with a written numeral
  • Count up to 20 objects one at a time, giving each object a number name
  • Understand that the last number said names the total amount for a group of objects
  • Understand that each successive number name refers to a quantity that is one larger
  • Count to answer “how many?” questions about as many as 20 things arranged in a line, a rectangular array, or a circle, or a scattered configuration
  • Count out a set of up to 20 objects
  • Review identifying whether the number of objects in a one group is greater than, less than, or equal to the number of objects in another group
  • Review comparing two numbers between 1 and 10 presented as written numerals
  • Compose and decompose numbers from 11 to 19 into tens and ones and further ones. (E.g. use concrete materials to make groups of ten and ones) by using objects or drawings and record each composition or decomposition by a drawing or equation (e.g., 18= 10+8); understand that these numbers are composed of ten ones and one, two, three, four, five, six, seven, eight, or nine ones.
  • Continue to work towards goal of fluently adding and subtracting within 20 using +1, -1, +0, -0 strategies.

Carroll County Public Schools Video Support

Ten Frame
Ten Frames

Numbers to Ten
Numbers to Ten

Using Ten Frames
Modeling With Ten Frames

Solving Addition Problems
Solving Addition Problems

Solving Subtraction Problems
Solving Subtraction Problems

Modeling Problem Solving
Moldeling Problem Solving

Ways Parents Can Help

  • Practice reading numbers as they appear in the world around you with your child.
  • Practice counting forward beginning with numbers other than 1.
  • Use the words after, before and between when talking about numbers. (I.e. What number would come after __?)
  • Use objects around the house (buttons, macaroni, pennies… to show two numbers up to 20 and compare the groups using the terms greater than, less than or equal to.
  • Use objects to show numbers 11-19 as a group of ten and some ones (i.e. 16 is 1 group of ten and 6 ones).
Some Support Sites


Key Vocabulary to Know


As many as


Count backwards

Double ten frames

Greater than


Fewer than



Less/Less than

Missing part

More/More than


Numbers 0-20

Number line

One less

One more



Put together




Take apart

Ten frame