Because today students will be using both addition and subtraction to solve a series of comparison problems, the warm up today will be a review of subtraction.
I ask students to take out their math journals and solve the 3 problems I write on the board. I write 38 - 12=, 17 - 9 = , 25 - 14 = . I give students a few minutes to solve the problems. Then I ask for volunteers to come up one at a time and show us their solutions. I ask students to explain how they solved the problem as well as give the answer.
I ask students to solve a few partners of 100 subtraction problems. I ask students to write the responses in their journals.
I say 100 - 50, I pause for students to write the response and then I ask for the answer, I repeat this with the next two problems., 100 - 80 =, 100 - 40 =.
I tell students that we have been reviewing subtraction because today they may need to use subtraction to solve some problems about the weather.
I ask students to come to the rug for the next part of the lesson.
I begin today by reading the students a short book about weather. The book: "Sunshine Makes the Seasons," by Franklyn M. Branley tells about how the weather is not the same everywhere at once (especially the beginning and ending of the book).
I ask students how many have ever traveled to somewhere by plane and found that the weather was different when they got there? I tell them that in our country Florida is about 24 hours of driving from Maine. I ask how many days that is? I ask students if they can find Maine and Florida on the classroom map. I tell them that if they got in a plane they could be there in 3 hours, but if they drove in a car it would take until tomorrow to get there, driving all night.
Now I ask them if they have ever traveled to Florida in the winter? Do they remember what the weather was like when they got there? (warmer than Maine, summery, etc.). I tell them that I gathered some temperatures for the past week from Maine and from Florida. I found the high temperature for each day and the low temperature for each day and today we are going to compare them.
I post the chart for everyone to look at. I point out the column headings, and how to find the high and low temperatures for each place for each day. Do the temperatures look the same? What is different about them? I let students make comments about what they notice.
Now I say, "ok, I have written a couple of math questions to see if we can figure out how much warmer Florida was on a certain day. I am going to hand you a paper and ask you to return to your seat and find your pencil. You may go quickly to your seat as soon as you have the paper." I hand each student a paper and then I ask them to look at the first question. I have a student read what they are looking for. I ask for someone to give me the first temperature. I make sure everyone knows where they found the information. We all record it on our paper. We continue to work the first problem together. We create a number sentence and then I ask students what strategies they might use to find the answer to the number sentence. (I encourage them to think about writing the numbers in columns, adding or subtracting tens and ones, counting up or back, using a number line, etc. I try not to encourage tally marks at this point in second grade.)
When students have solved the problem we compare answers and solutions.
We do the second problem together in a similar fashion.
I then explain to students how they will finish the paper independently. I have a challenge page for those that finish early.
When students have finished the paper and are mostly working on the challenge page, I bring the group back together. I ask students to look at their papers. I tell them we will share answers and solutions to the problems on the page and then I will ask for volunteers to share a couple of their problems for the rest of the class to solve.
I know that we will only be able to share 1 or 2 of the student problems, but I can save the other problems for warm ups for tomorrow.