12.12Adding Two 2-Digit Numbers Practice

COMMON CORE STATE STANDARD
1.NBT.4 - Number and Operations in Base Ten
Use place value understanding and properties of operations to add and subtract.
Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
BIG IDEA
Students will practice adding two 2-digit numbers using strategies they have learned within this unit.
Standards of Mathematical Practice
Make sense of problems and persevere in solving them.
Reason abstractly and quantitatively.
□Construct viable arguments and critique the reasoning of others.
Model with mathematics.
Use appropriate tools strategically.
Attend to precision.
Look for and make use of structure.
□Look for and express regularity in repeated reasoning. / Informal Assessments
□Math journal
□Cruising clipboard
Foldable
□Checklist
□Exit ticket
Response Boards
Class discussion
handout
PREPARING FOR THE ACTIVITY / MATERIALS
  • “Problems involving the sum of 2 two-digit numbers will usually produce a wide variety of strategies. Some of these will involve starting with one or the other number and working from that point, either by adding on to get to the next ten or by adding tens from one number to the other” (Van De Walle, 2013, p.223).
  • For more information about what is expected by students at this grade level, see p. 6 – 7 of Draft K–5 Progression on Number and Operations in Base Ten
  • For Setting the Stage: 1 deck of cards are needed per pair of students. (Face cards should be removed, and Aces are 1).
  • Two number cubes per pair or group of 4. (It would be ideal if one number cube was labeled 1 – 6, and the other one was labeled 4 – 9).
  • Put Place It! Recording Sheet in sheet protector so that students can re-use it for different games.
/
  • Deck of cards (one/pair)
  • Hundreds chart
  • Base-ten blocks
  • Response boards
  • Chart paper
  • Number cubes
  • Place It! Recording Sheet
  • Sheet protector
  • Dry erase markers

VOCABULARY
  • Add
  • Tens
  • Ones
  • Equation

SETTING THE STAGE
Procedures
1.Pair up students. Distribute a deck of cards. Have students engage in Addition War.
  1. Player 1 deals all the cards between the two players.
  2. Students hold their stack face down in front of them.
  3. Each player flips over a card.
  4. The first student to call the total of both cards wins both cards. If students say the total at the same time, split the cards.
  5. The player with the most cards at the end of the round, wins.
/ Guiding Questions
  • What happens to the tens place when you add a ten to a number?
  • What happens to the ones place when you add a ten to a number?
  • Is it easier to add numbers when you break one apart into tens and ones? Why?
  • Is there another way you could break the number apart?

EXPLORE THE CONCEPT
Procedures
  1. Play Place it!
  2. This is a game for 2 to 4 players. The object is to get blocks that have a total value close to 100 without going over.
  3. A player rolls the number cubes and decides how to read the digits that come up as a two digit number.
  4. The player draws base-ten blocks to represent the number on the Place It! Recording Sheet.
  5. The other players each take a turn rolling the number cubes, deciding on 2-digit numbers, and recording on their own mats to show the numbers.
  6. Play continues for a total of 2 rounds.
  7. A player may reject any 1 throw if it seems that either of the 2-digit numbers would add too much to his or her sum. Each player may do this only once during a game. The player must count a reflected throw as 1 of the 2 rounds by giving it a score of 0 for the round.
  8. After 2 rounds, players find the total values of their numbers and record the strategy that was used to solve the addition problem.
  9. Whoever gets closest to 100 without going over is the winner.
/ Guiding Questions
  • Which strategy do you like better? Why?
  • How can we record this strategy?
  • Which strategy did you use for this problem? Why?
  • How did you decide which 2-digit number to use on each roll?
  • Were you ever sorry that you didn’t use the other number you rolled? Explain.
  • Did you ever decide to reject a throw? If so, why?
  • How did you decide whose sum was closest to 100?
  • Do you have a strategy for winning this game? Do you think it will always work?

REFLECTION
Procedures
  1. Distribute exit ticket. Allow students to solve problem.
  2. Have students share the strategy they used to solve the problem and explain how and why they chose the strategy.
/ Guiding Questions
  • Which strategy did you use? Why?
  • Can you explain the strategy you used?

Source: Hirschhorn, D. (2000). …the Super Source – Base Ten Blocks. Vernon Hills, IL: ETA Cuisenaire.

Grade 1Unit 12: Block 12

Name: ______Date: ______

Exit Ticket

Directions: Add the following numbers. Show the strategy you used to add the numbers in the space provided.

48 + 35

Name: ______Date: ______

Exit Ticket

Directions: Add the following numbers. Show the strategy you used to add the numbers in the space provided.

48 + 35

Name: ______Date: ______

Place It! Recording Sheet

Round / Number / Base-ten representation
1
2
Work to show adding the numbers from Round 1 and Round 2

Grade 1Unit 12: Block 12