Magic of Adding Tens

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SWBAT add groups of tens within 100 and bundle ten's partners together to make tens.

Big Idea

Students should have mastered adding numbers within 10 in first grade. The Common Core stresses adding bundles of tens in second grade.

Getting Started

10 minutes

Today students start by reviewing the Ten's Rhyme they learned yesterday. They practice the rhyme with choral reading. Next students hold up both hands (a bundle of 10). I ask them to hold up 2 fingers. How many more to make a bundle of 10? (8). I repeat this several times to get students familiar with the ten's partners.

Next I put the following number sentences on the board for students to solve in their math journals:

 6 + 4 =         and  10 - 6 =   I ask students to solve the problems independently. I ask for a volunteer to explain how they found the answer to the 2 problems. I usually take 3 - 4 different solutions. I want students to make sense of the problems on their own first, and solve them (MP1), before students share. I expect that students will count up, count down, recognize it as a fact family they know automatically, use a number line, or number grid to solve the problems. 

Next I ask students what they notice about the 2 problems. I take comments from the students and reinforce any suggestions that the two number sentences are a fact family, or opposite of each other or the same numbers.

I ask for another ten's partner and write it on the board. I ask if anyone can come up and write the subtraction number sentence for this ten partner.

I give students a quick stretch break before beginning the main part of the lesson.

Teaching the Lesson

25 minutes

I tell students that today we have already looked at the ten's partners. Today I am going to ask them to create pictures with things in bundles of ten. They must use 2 colors in their pictures to show the partners that come together to make 10. I demonstrate 4 red apples and 6 green apples together in a bundle. I ask students to tell me the number sentence for this picture. 

We practice several more together with students suggesting what to bundle and drawing a quick sketch and number sentence. 

Next I hand out a page with several bundles for them to fill. I tell them they can fill more than one page with bundles of 10, but each bundle can only hold ten. 

I give students about 15 minutes to draw their pictures. Creating Bundles of Ten

I do not double side the paper because in the next section students will be putting bundles together to add bundles of 10 to get 100. 

I do this activity with all students because even students who are already adding larger numbers are not always clear about what they are actually adding. For them to really see 100 is important.

The Next Step

20 minutes

In this section of the lesson I want students to actually see what 100 looks like, and to relate that to our ten's partners. I want students to look at the structure of bundles of 10 and how they combine to make 100. I hope they will see the relationship between the structure of partners of 10 and the structure of partners of 100. (MP7)

I ask each student to label the top of their bundle with their name, written in a color. I then ask them to cut the 3 bundles apart on each page. I know that each student has made at least 2 pages (or 6 bundles of objects).  Next I arrange the students in groups of 2. Their task is to see how many bundles of 100 they can create using their bundles together. I tell them they may have extras. I ask them to write down how many bundles came from partner A and how many from partner B. They glue their bundles of 100 onto large paper.

To wrap up today, I show a few of the new bundles of 100.Bundles of ten combined to bundles of 100 We talk about how we had little bundles of 10 but now we have put them together to get big bundles of 100. We count the number of bundles by ones (1 - 10) and then we count by tens as we check that each bundle is a bundle of 10 so we count 10, 20...100. Counting by tens up and back using our new bundles of ten pictures will help students to have a better understanding of what 100 is, and will prepare them for later addition and subtraction based on place value.