Today I begin by reviewing how addition is the opposite of subtraction. I put 4 subtraction number sentences on the board:
26 - 12=
19 - 11 =
22- 9 =
27 - 14=
I ask students to write in their math journals the addition sentences that go with the subtraction sentences and to solve both. I am asking them to make sense of the two problems and then to solve them (MP1). When students show with a thumbs up that they are mostly done, I say “Now that everyone has at least 2 of the problems done, lets share what we have done.” This validates that everyone has tried and done part of the task and it is alright not to be completely done. I ask for volunteers to come up and write the addition sentences they found. There will be 2 addition options so I allow for a second round of students to come up and tell what they have done. We talk about why both of these models work.
I remind students that they can use an addition number sentence to help them figure out a subtraction sentence or visa versa. Here I am introducing another way to make sense of math problems so students can solve them independently (MP1).
Today I will have 3 homogeneous working groups. Students will spend about 15 minutes at each center. Today students will be working to solve math problems by modeling with mathematics (MP4), making sense of problems (MP1) and choosing the correct tools to measure (2MD.A.1)
I ask students to return to their seats. I ask for comments about the treasure hunt. How many students finished? Did they figure out the message? (If students are not done, I allow students to finish the next morning and ask others to keep the message a secret.)