• Observe students playing the Parking Cars game to understand which strategies they are comfortable using to make ten.
• As students model and record their solutions to the story problems, note which students are ready for extension activities and which students might benefit from guided practice in a small group.

The first activity in this lesson is intended to get students thinking about how many ways they can make ten when they are adding. As they are thinking about what numbers they need to roll in order to fill their ten-frame parking lot, they are finding missing addends. This is appropriate practice leading into the story problems they will solve, which require multiple addition and subtraction strategies. The second part of the lesson gives students practice in choosing operations to solve story problems about cars entering and leaving parking lots.

“When you go to the store with your mom or dad, where do you park? That’s right, the parking lot. Today we are going to explore addition and subtraction with the help of some cars and a parking lot. You will use these (hold up cars) as the cars and this ten-frame (hold up the ten-frames page) (M-1-3-1_Ten-Frames.doc) as the parking lot. How many cars can park in this lot? Yes, ten. We are going to begin with a game called Parking Cars.

“You will be playing this game with a partner. Each of you will have ten cars and one parking lot. You will share a number cube. When it is your turn, roll the cube and put that number of cars in your parking lot. If the number you roll is greater than the number of empty spaces in your parking lot, you lose your turn. So, if you have 2 empty spaces in your lot and you roll a 4, you lose your turn. Four is greater than 2. You must roll a 1 or a 2 in your next turn in order to park more cars. The goal is to be the first person to fill your parking lot with ten cars. You can decide who starts the game by each rolling the cube once. The person with the highest number goes first. I will give you about 15 minutes to play, so when you finish one game you can start over with another game. Take turns going first.”

Ask a volunteer to play a few rounds with you to model how the game is played. Pair up students and give each pair one number cube, 20 cars or chips, and two ten-frames (M-1-3-1_Ten-Frames.doc). Walk around to observe students. Notice which students are able to quickly recognize the missing addend (how many spaces they need to fill to make ten).

Ask questions such as:

• “If you have seven cars in your parking lot now, what numbers could you roll to fill the empty spaces?” (3, or 1 and then 2, or 1 and 1 and 1)
• “I see that you have three cars in your parking lot. Can you finish filling it with only one more turn?” (No, because I need seven more cars and I can’t roll anything higher than a six. So, I need at least two more turns.)
• “What is the fewest number of turns it would take for someone to fill his/her parking lot?” (Two, because s/he could get a 5 and a 5, or s/he could roll a 6 and then a 4.)

When students have only a few minutes left to play, give them notice that they should finish the game they are playing and not start a new one. Gather the students together and tell them, “We have just been practicing adding and subtracting with our cars. Does anyone remember what these words mean?” Call on a few students to answer. “We are going to work with number stories next. When solving a number story, we create a number model. A number model uses numbers and symbols.” On the board, easel, or chart paper, write the word “add” and ask students if they know what symbol or sign means adding (+). Place the addition symbol next to the word “add.” Repeat this process with “subtract” (–) and “equals” (=).

Collect the number cubes and ask students to each keep ten of the cars and one of the parking lots they used for the game. Give each student a piece of paper and a pencil or a whiteboard and a marker to use for writing the appropriate number sentences. They will be working independently for the next activity.

“Now I will tell some stories and you will solve the problems using the cars and the ten-frame parking lot. Let me show you an example.” Model solving a number story. Be sure to model not only solving with the cars, but also creating the number model. “Now it’s your turn. Listen carefully to each story to decide if you will be adding or subtracting cars from your parking lot. Work with your partner and use your cars (or chips) and ten-frame parking lots to show your work. Write a number sentence that tells how you solved the problem using addition or subtraction.” Go over each problem with the whole group after it is finished. If it looks like students are having trouble getting through the problems, use a think-aloud strategy to walk through the first few problems step by step.

Tell stories that require a variety of solution strategies. For example, simple addition:

• “Your parking lot has 6 cars. Three more cars pull in and park. How many cars are in your lot?” (6 + 3 = 9)
• “Your parking lot has 3 cars. Six more cars pull in and park. How many cars are in your lot?” (3 + 6 = 9)
• “Your parking lot has 3 cars. Two more cars pull in and park. Then 4 more cars pull in and park. How many cars are in your lot?” (3 + 2 + 4 = 9)

Simple subtraction or “take away”:

• “There are 8 cars in your parking lot. Five leave. How many remain?” (8 – 5 = 3)
• “There are 9 cars in your parking lot. Six leave. How many remain?” (9 – 6 = 3)

Missing addends:

• “Your parking lot has 4 cars. How many more cars will need to park in your lot for it to be full?” (4 + 6 = 10, or the inverse operation 10 – 4 = 6)
• “Your parking lot has 5 cars in it. An hour ago your parking lot had 9 cars. How many cars left your parking lot?” (5 + 4 = 9, or the inverse operation 9 – 5 = 4)

Comparisons:

• “I have 3 cars in my parking lot and you have 9 cars in yours. How many more cars do you have?” (We both have 3 and then the student has 6 more; or 3 + 6 = 9; or 9 – 3 = 6.)
• “Your parking lot has 7 cars in it. My lot has 9 cars in it. How many more cars are in my lot?” (The 7 in the student’s lot match up with 7 in the teacher’s lot. Then the teacher has 2 extra; or 7 + 2 = 9; or 9 – 7 = 2.)

Multiple operations:

• “Your parking lot has 6 cars parked in it. Four cars drive out. Five cars drive in. How many are parked there now?” [(6 – 4) + 5 = 7]
• “Your parking lot has 5 cars in it. Three cars drive in and park. Four cars leave. How many cars are in the lot now?” [(5 + 3) – 4 = 4]

Observe students as they model and record their solutions. Students could be selected to show their work on an overhead projector or other projection device.

When students demonstrate an understanding of the activity, choose some to create story problems for their classmates to solve. Their stories may be very simple or quite challenging. This is appropriate practice.

As students tell their own stories and listen to their classmates offer solutions, ask the storytellers to compare their own solutions with those of classmates. Did you each write the same number sentence? Did you write different number sentences but still get the same answer?

Extension:

• Expansion: When students are confident solving addition and subtraction stories with ten cars, give each a second ten-frame parking lot. Students could work independently or with a partner to solve problems with greater numbers of cars in two parking lots.

Tell stories such as:

• “Patrick has 2 parking lots. He has 9 cars in one and 6 in the other. How many cars are in the lots altogether?” (9 + 6 = 15)
• “Donny has 7 cars parked in one of his lots and 8 cars parked in the other. If 5 more cars need to park, does Donny have enough parking spaces for them?” (Yes, because 7 + 8 is 15. He has 20 spaces and 15 + 5 = 20.)
• “Maria has a ‘Lot Full’ sign on both of her parking lots. Five cars leave one lot and two cars leave the other. Three cars have been waiting for spaces. After they park, how many more cars can Maria let park before she has to put up the ‘Lot Full’ sign again?” [20 – (5 + 2) = 13 and 13 + 3 = 16 so 4 more cars can park because 16 + 4 = 20.]
• Routine: Have students keep a math journal in their desks. As students arrive, ask them to take out their journals as part of their morning routine and write solutions to problems you post on the board. To continue reinforcing the relationship between addition and subtraction, draw a large ten-frame on the board and draw dots in some of the spaces. Ask students to copy the drawing in their journals and then write at least one addition sentence and one subtraction sentence that could describe the model. For example, draw this ten-frame.

Tell students this is a parking lot with 10 parking spaces. The red dots stand for cars. There are 6 cars parked in the lot. They must figure out how many additional cars could fit in the lot. Then they must write an addition number sentence using the numbers from the problem, 6, 10, and the number they figure out (4). Students could write 6 + 4 = 10 or 4 + 6 = 10. Then tell students to write a subtraction number sentence using the numbers from the ten-frame. Students could write 10 – 4 = 6 or 10 – 6 = 4.

An alternative would be to have students write a story problem about the model, such as, “Six cars were parked outside the store. Four more cars filled the empty spaces. How many were there altogether?”(The story need not be about cars and parking lots if students choose to offer creative alternate scenarios.)

• Workstation or Small Group: Prior to this activity, print student copies of the Number Sentences activity sheet (M-1-3-1_Number Sentences.doc). Print each page back-to-back, and write the answers in the blanks on one side to create a self-checking activity. Laminate the pages and provide dry-erase markers to save paper.

Students will work independently or with a partner to complete number sentences, using the cars and ten-frames to help find a solution. Students should choose a number sentence, make up a story about cars that models the problem, and solve to find the missing number. Tell students to write the missing number in the blank and then turn the paper over to check their answer.