This is an easy plan for a sub as long as students have had experience with "secret number" triangles (secret numbers lesson) and with group work. When "secret number" triangles were introduced many students found them very challenging, but now, with the work we've done exploring integer number relationships (How do we know lesson) I expect them to have greater success. This lesson also gives them the opportunity to create their own triangles as long as the sums meet a given criteria (+, -, or 0). I leave a general explanation of what "secret number" triangles are, but ask that the sub circulate and ask students to show him/her how they work. Students love explaining things to the sub.
As students enter the Warm up secret numbers 2 is on the screen. It shows two triangles and students are told that a secret number is hidden at each vertex of the triangle. On each side of the triangle is written the sum of the two numbers at each end. Students are asked what the secret numbers could be? They are also told that these two problems are the first two problems from their homework. (This gives them a little more motivation to do the warm up now). When I have a sub I always leave an answer key for the Warm up secret numbers 2 answers. I tell the sub to let students work for about 7 - 10 minutes. I don't expect everyone to solve both triangles within that time and I want them all to experience some level of success so they are motivated to continue, so I tell the sub to ask a student just for the top "secret number" and let the rest of the class figure out the rest from there. This still gives students practice with integer sums and the satisfaction of figuring something out.
For the remainder of class students can work together in their math family groups on their homework secret numbers 2. The homework has several "secret number" triangles with the side "sums" given. They have to find the "secret number" addends. The homework also includes several triangles that ask them to find secret numbers that would produce the given criteria for the side "sums". I don't give the numbers, just whether the sum is positive, negative, or zero. I tell students to have their math family group members check that their triangles work. I tell the sub to tell them that he/she doesn't know the answers so if anyone thinks they have solved it to call him/her over and show how it works.
If students finish early I suggest that the sub have the student try to create a challenging "secret number" triangle for the class, which he/she can put on the board.
Having students work together with integer sums helps them internalize the number relationships and patterns that will be useful in improving their integer number sense and fluency.