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 020 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 Frames
Numbers to Ten
Modeling With Ten Frames
Solving Addition Problems
Solving Subtraction Problems
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 1119 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 
Add/Addition
As many as
Compare
Count backwards
Double ten frames
Greater than
Equal
Fewer than
Join
Least
Less/Less than
Missing part
More/More than

Most
Numbers 020
Number line
One less
One more
Partpartwhole
Plus
Put together
Same
Separate
Subtract/Subtraction
Take apart
Ten frame
