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Module 4 - Activity 2: Benchmark Numbers and Making 10s

Benchmarks are numbers that are useful in making estimates such as 5, 10, 25, 50, or 100. Children need to understand and visualize numbers around benchmarks. Important benchmarks for grades K to 2 are 5, 10, 20.

watch  Video: Make-a-Ten 

In this video, we discuss the prerequisite skills that children need in order to use the make-a-ten strategy. Being able to make-a-ten seems like it is a simple skill, but in fact it's actually a very sophisticated strategy for children in grades K to 2.

As you watch this video, think about the following questions:

  • What are the three prerequisite skills for making a ten?
  • How does children's ability to compose and decompose numbers help them with these prerequisite skills?

Pull Down Notation

In the video, you might have noticed the writing on the board. Terry recorded solutions to 9+6 using "pull down notation." This notation illustrates how children might describe how they composed and decomposed numbers using the make-a-ten strategy. Three derived facts that involve making tens for 9+6 are shown below.

Pull down notation for 9+6: Example 1: The expression nine plus six is written. A caret symbol is used to show the six is decomposed into one plus five underneath it and the new expression nine plus one plus five is written below. A caret symbol denotes the nine plus one is composed to make ten resulting in a new expression ten plus five written underneath the previous expression. A caret symbol denotes the ten plus five is added and the number fifteen is written below. Example 2: The expression nine plus six is written. A caret denotes the nine is decomposed into five plus four and the new expression five plus four plus six is written underneath. A caret denotes the four plus six makes ten and the new expression five plus ten is written below. A caret symbol is used to show five plus ten is added and the number fifteen is written below. Example 3: The expression nine plus six is written. The six is decomposed into five plus one and the nine is decomposed into five plus four. The new expression written below is five plus four plus five plus one. The two fives are added to make ten and the four and the one are added to make five. The new expression ten plus five is written below. Ten plus five are added and the number fifteen is written below. 

PLC Action  Unpacking the Make-a-Ten Strategy 

As a PLC, write a join (result unknown) problem for 7+6=?.

There are three typical derived fact strategies that involve making tens when students solve 7+6. One involves decomposing the 7, one involves decomposing the 6, and the third involves decomposing both the 7 and 6. Discuss with your PLC what these derived facts might look like, and illustrate them using the pull down notation.

For each of these make-a-ten strategies, how are the prerequisite skills listed below used?

  • Knowing the different ways to make 10
  • Knowing how to decompose any single digit number
  • Knowing that 10 plus any single digit is that teen (i.e., 10+9=19)