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This connects to our class from quite a while ago, while we were learning about different addition and subtraction strategies within whole numbers. What interested me most about our time spent focusing on addition and subtraction was just how many strategies there are that students can use to solve these problems. I knew prior to this class that there were many strategies and ways to solve mathematical problems, but I would say the number of strategies I was exposed to through this course showed me just how many I had never seen or used before. This was extremely interesting to me, and made me more excited to be a teacher in the future.

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Adding and subtracting within 100

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1. ***Provide some example problems with addition and subtraction and have students solve them***
2. Ask the class as a whole if they have any strategies to solve addition and subtraction questions within 100.
3. Have students draw a number line as practice before playing the game, and draw one as an example so they know what it should look like. As if they have any observations about the number line.

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Some good questions to ask students to discuss with their partners following this activity would be:
1. Compare where your chips are located currently on the number line, which partner was closer to winning?
2. Which partner moved further from the center of the number line?
3. What strategy did you use to quickly add or subtract during this game?

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1. Students will be able to add and subtract numbers within 100.
2. Students will be able to compare two numbers within 100.

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Objective

Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

MA2-NBT-B-5

Materials

Paper

Pencils

Rulers

Hundreds Charts

Decks of cards (or homemade cards) Numbers 2-10

Dice

Spinner with 0-10

Colored chips

Index cards

Number Line Strategy

Use a piece of paper and a ruler to draw a horizontal line across the page to make a number line. Assign each student a two-digit number as the beginning number on the number line and instruct them to make 20 vertical marks and write numbers under each mark until they reach the final number. For example, the student might start at 23 and end at 43.

The game starts with both players placing a chip on the middle number. In our example, that would be 33. The object of the game is to work your way to one end of the number line. The player on the left (Player A) will subtract and the player on the right (Player B) will add.

Let's say that Player A is on 33 and spins a 5. He would subtract 5 from 33 and place his chip on 28. Player B, who is also on 33, spins and gets 2, so he moves his chip to 35.

As a defensive move, the player may decide to move the opponent's chip at his turn instead of his own to prevent him from winning. Addition, subtraction and strategy!

It's in the Cards

Target: A pair of students sits facing each other with a deck of cards in between them. Cards should only have numbers 2 through 10. (No face cards, jokers or aces). Give the students a "Target" number. A player takes a card from the top of the pile and places it face up in front of him in a row. Take turns doing this. Each player has his own row of cards. He adds each number chosen onto his personal total. The player who reaches the target number first is the winner.

Beat This: A pair of students sits facing each other with a deck of cards with only numbers 2 through 9. (No aces, face cards or jokers). This time, each player takes two cards and arranges the cards in front of him so that they form the largest possible two-digit number. So a 6 and an eight would be 86. Then decide which of the two students has the biggest number. The student with the biggest number adds his number with his opponent's number. The opponent takes the two numbers and subtracts. The answers can be used as points for the players or just give one point for the holder of the highest number.

Hundreds Chart

Point to a number on the hundreds chart and ask how many more till we reach 100. Then, have a "Math Talk" to discuss the strategies that were used. Did you count one number at a time to reach 100? Did you count rows of 10? Did you subtract mentally?

Put your finger on the number 4. Where will you be if you add 9? Did you have to count or did you add mentally? What if you were on 23 and added 9? Can you do that without counting? Observe the students to see who can recognize a pattern on the chart when 9 is added.

Select two teams of students. Use a spinner and the Hundreds Chart. Which team can reach 100 first? If they find an answer without counting they can move forward one extra space.

Which One Is Not the Same?

Write a number sentence on the board. Then write three number sentences under it making one of them incorrect. For example:

21+ 13

20+ 14 22+ 15 19+15

Have students write their own problems on a file card and trade with a partner. When the two students have solved each other's cards, they move on to a different partner.

Roll the Dice

Working with partners or in small groups, each student writes the numbers 1 through 12 on a piece of paper. Each player takes a turn rolling the two dice. The player may choose to add or subtract the amount rolled. Then the player says the math fact and crosses out the answer on his paper. The winner is the one who crosses out every number on his paper. Or you can set a time limit and see who has crossed out the most when time is up.

For example: Player One rolls a 4 and a 2. He says, "4+2= 6". Then he crosses off the 6 on his paper. But if the six is already crossed off he could say, "4-2=2" and cross out 2.

References

Kuhns, Catherine and Lasater, Marrie. Common Core Math in Action. Crystal Springs Books, 2013.

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Fun Activities to Reinforce 2nd Grade Addition and Subtraction Skills

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Your second graders have successfully learned how to add and subtract, but now you want to strengthen their abilities. This list of entertaining and educational games and activities will engage your students while giving them a firmer grasp on basic math skills.

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1. Draw a number line starting at 0, and ending at 100.
***TIP: THIS WOULD BE DONE EASIEST IF THE NUMBER 50 IS PLACED IN THE CENTER OF THE NUMBER LINE FIRST, AND ONE PARTNER THEN NUMBERS THE NUMBER LINE 0-50, AND THE OTHER 50-100***
2. Once the number line is complete, both partners will place their chips on the number 50 (the center of the number line)
3. One student will be playing this game using addition, one will play using subtraction (students can determine between themselves who will be addition and who will be subtraction)
4. Players will then begin the game by spinning the spinner. The student playing with addition is playing to get their chip to 100 more quicly than the player with subtraction gets their chip to 0. As they spin the spinner, the number selected determines how much each player adds/subtracts.
5. Students take turns spinning the spinner and moving their chips until one of them reaches their end of the number line.

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1. A piece of paper (one per two people)
2. One pencil per two people
3. Spinner with numbers 0-10 (one per two people)
4. One ruler per two people
5. Two chips (one per person, two different colors per group)

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Use addition and subtraction within 100 to solve one and two-step word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g. by using drawings and equations with a symbol for the unknown number to represent the problem.