# Another Visit to Double-Digit Work

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## Objective

SWBAT apply and explain place value strategies for solving double-digit addition and subtraction problems.

#### Big Idea

Students should be able to explain their strategies for solving problems to 100 using place value strategies.

## Warm Up

10 minutes

I begin today by handing out a 25 problem quick math fact practice sheet. I give students 3 minutes to complete as much of the page as they can. I am looking for student automaticity with addition and subtraction. I generate the page at MathFactCafe.com.

After 3 minutes I ask students to stop and exchange their pencil for a marker. We now correct the pages together. By using marker, students may not change their original answers so I can assess their fluency, but by correcting their own work, they become more aware of their own needs in developing automaticity with basic facts.

## The Double Digit Game - 2 ways

25 minutes

I begin today by gathering the students on the rug. I have decks of number cards 0 - 9 for each group of 3. I also have paper, clipboards and pencils, and manipulatives.

I tell students that we will play an addition game for 10 minutes and then a subtraction game using the same process.

I tell them that the first partner will draw 4 cards and make 2 2-digit numbers to be added together. All 3 members of the group will solve the problem independently using paper and pencils, or tens frames, or base ten houses, or blank number lines.

After everyone is done they will compare answers. If everyone has the same answer then they can assume it is right and give the team 3 points. If anyone has a different answer, then each child will explain what he/she did and students will determine the correct answer (MP3). Any answers that were correct will earn the team a point. At the end of the addition "round" the team will tally its points.

I will ring the bell after 10 - 15 minutes of play, and tell students we will now switch to subtraction. I remind them to stop, look, and check ( a strategy they have used in previous lessons to remember to stop, look at the ones place and check the larger number so they know if they need to borrow or not.) The team will earn points the same way.

At the end of the subtraction round the team will add their addition and subtraction points to get a total. I ask students to tell me the totals. Now I ask all students to return to their seats.

## Closing

20 minutes

I ask each student to add up the totals for all the groups. We check our work and agree on a final total. I write a big sign on the board saying We Collected ______  Addition and Subtraction Points!!!

I close with a short independent practice page with 2 addition and 2 subtraction problems for students to solve and hand in for me to assess understanding.

The problems I post are:

67 + 25 =

34 + 45 =

62 - 44 =

78 - 36 =