SWBAT compare their work to comparison problems for accuracy, and explain why their addition or subtraction strategies worked.

Students need to be able to explain the strategies they use to solve problems, and also they must understand the importance of checking their own work.

15 minutes

I put the following problem and solution on the board.

*I am 65 inches tall. My friend is 75 inches tall. How much taller is my friend than me? 65 + 75 = 5+5 = 10, and 6+ 7 = 13 and because 10 + 13 = 23, my friend is 23 inches taller than me.*

I ask students to look at my work. *What do you notice about my work?*

I listen as students make suggestions about what is correct or incorrect about my work. When we finally come to a consensus that I added, when I should have subtracted, I ask how I might have known what to do?

If no child suggests looking at the words that might help me (in my class we call them the *street sign* words math street signs.docx), I will lead students to look at the chart we made earlier which displays key words that help me to know which operation to use.

15 minutes

I tell students that today they will at some solutions from their classmate's practice page from yesterday’s lesson. I copied some of the solutions from different partnerships – some correct and some incorrect, for students to work with, onto a separate document for this lesson.

I tell students that they will be the teacher, and they need to correct this student work on their own. I alert them that some of the problems may be correct, and some may be incorrect. Students are told to mark work as correct, and redo problems or circle any place where they think there might be a mistake. They should be ready to defend their corrections. I tell them they will have 15 minutes to go over the work and then they will partner up with others to defend their corrections.

I ask for a student to repeat the directions as this is something we have not done before and I want to check for understanding before I let students work independently.

15 minutes

Students work for 15 minutes independently correcting the papers they have (which are copies of some of the student work from yesterday’s lesson that I have copied onto a master page so no one's work is being shared).Student Work I purposely chose examples that are incorrect in one way, such as the person added where they should have subtracted, or they did not attend to place value to see if students could reason abstractly and quantitatively about the problems as they try to make sense of what they need to do (MP 1 and MP2).

As students are working, I circulate around the room listening as students explain their thinking. Deciding Which is Correct

15 minutes

Today’s closing is longer that usual because I will ask students to critique each other’s solutions. (MP3). I ring the bell and tell students that I am going to partner them into groups of 4. They will bring their papers and compare what they have found as they corrected the papers. They will need to discuss any problem that all 4 did not agree on. They should work problem by problem, see if all 4 people agreed on whether the answer was right or not, and then if it was not right, how did they solve it, what can they see that the person might have done incorrectly, and what did they do to find the correct answer?

I give students about 15 minutes to discuss the problems. I circulate during this time to listen to student thinking, and to provide support as needed.