I begin today’s lesson by assessing student command of automaticity adding and subtracting 0, 1, 2, and 3, using a two minute number facts quiz. There are 25 mixed addition and subtraction problems on the page.
At the end of the 2 minutes, I ask students to take out a marker to correct their own paper. I read the problems aloud and take student answers, which I then echo. If incorrect, I'll ask, "Does anyone have a different answer?" Generally someone will have another answer, and I'll ask how they know it is true. Once we've established the correct answer, I repeat the entire problem. I collect the papers for closer review later before going on to the next part of the lesson.
During the previous lesson students gathered data and created a way to share that data. Today we will use the data to make comparison problems. I hang up two of the charts and pose the problem:
“How many more bugs with legs did the first group find compared to the second group?”
I ask how we might figure this problem out, and what information we need to do the work. Students make some suggestions and we explore these, using our best mathematical thinking and vocabulary (MP3).
I show students how I can make a tower of linking cubes to represent the groups of tens and ones for the first group, and then a tower to show tens and ones for the second group. Now I can count the difference between the two towers to show how much more one group has than the other.
I tell students that today I will have the groups combine and I will raise several questions for students to solve using the data from each group. They need to think about what they already know about the question, such as how much each group has, and then find a way to compare the two numbers (MP2). I ask students to think about this important question:
If we are comparing two groups, can our answer can be bigger than the numbers we start with?
I create an example on the board for students to look at as they think about this question.
The students are now grouped and given a set of comparison questions to solve. They may use manipulatives, drawings and tally marks to complete the work. (MP4) I circulate around to assist groups with thinking by facilitating their use of strategies to use to solve their problems.
I call students together on the rug. I ask them to bring their solutions with them. I pick one of the questions and each group shares out their solution and how they found it. Students share out and are encouraged to comment on each other's solutions. We note that the answers are always the same or smaller than the starting numbers when we do comparison problems.