SWBAT use partners of ten to get to the next multiple of 10 and then use partners of 100 to get to 100

Automaticity with patterns that allow students to easily manipulate larger numbers is the aim of this lesson.

10 minutes

In the warm ups today I work on mental math with students. I want them to review the patterns they already know, such as partners of 10, partners of 100, doubles, halves, repeated addition and doubles plus 1.

My goal for this warm up is to have students work quickly to complete a series of oral problems as they attempt to build their fluency.

I have students take out a blank piece of paper. I tell them that I am going to dictate a series of addition and subtraction problems. They can write the problem, or just the answer. I tell them that to make it easier, they should write the letters A - N on their paper and write the answer next to each letter. We will check the answers together at the end. (I count to 15 between problems and then go on.)

A. 7 + 3

B. 16 - 8

C. 60 + 40

D. 3 + 3 + 3

D. 100 - 30

E. 9 + 9

F. 70 + 70

G. 17 - 7

H. 14 - 6

I. 100 - 50

J. 2 + 2 + 2 + 2

K. 80 + 20

L. 8 + 7

M. 13 - 6

N. 80 + 80

Together we go over the problems and students correct their own work with a marker. I ask students to go back and look at B, D,G, H, M and check how many of those they got right? These were the subtraction. I ask them just to hold up the number of fingers to show those that they got correct.

I bring students to the rug to review a game with them.

20 minutes

I welcome students to the rug and tell them that today they will play a game that most of them have played before but today we will use pennies and dimes rather than base 10 blocks. In this game they will use playing cards less than 10 (remove any cards over 9 from the deck). The first person will make a 2-digit number by drawing 2 cards and use the numbers on the cards as the digits of a 2-digit number. The second person will take pennies and dimes and count from this number up to 100. Together they will write a number sentence for the number on the cards + the total of the coins = 100. Students will then write a related subtraction sentence for the pair.

Example: Child 1 draws the cards 5 and 7. He makes 57. The second child takes 3 pennies to get to 60 and then 4 dimes. They write 57 + 43 = 100 and 100 - 57 = 43. I am hoping that students will see the structure of the related addition and subtraction problems as they build and write the problems (MP7)

I demonstrate the game several times until I am sure that students understand what is expected. Then I partner students up putting a stronger student with a weaker student to allow them to support one another. (The stronger students strengthens his/her understanding by having to explain to the weaker student and the weaker student benefits from the added instruction from a peer.)

I allow students to play the game for about 15 minutes while I observe and support struggling learners by helping to talk them through what they are actually doing as they build or write the number sentences. At the end of the game we meet on the rug to share some of our math sentences and to talk about anything that students may have found out as they played.

20 minutes

Students have just played a game with making 100 and then writing a related subtraction sentence. Now we will use that same strategy to go shopping.

I keep a collection of small toys in the room for math. These toys include small stuffed animals, bouncy balls, toy cars, etc. I divide the toys into 4 groups (for 4 stores). At each store I have set up the prices, the objects and the money.

The prices are all under $1.00. Students choose a toy and a price. They give the store keeper 1 dollar. The storekeeper must use pennies and dimes to count up to 100 from the price and then give the shopper his/her change. Students model with mathematics as they make change (MP4)

Students take turns being a shopper or a storekeeper. I have more than 1 storekeeper at each store so that students have several turns with both jobs.

As I circulate among the groups I demonstrate for students who are struggling, how to make the change by counting up. Students put the objects back in the store for someone else to buy after they are done buying them.