Time Machine Addition and Subtraction Freebie

Our district uses Go Math for our math curriculum.  This is our 3rd year since textbook adoption.  The curriculum is aligned with FL's Next Generation Sunshine State standards (NGSS); although, we are in the process of adopting the Common Core Standards.  One of the NGSS standards for 2nd grade is:

 MA.2.A.4.5: Recognize and state rules for functions that use addition and subtraction. 

Well, I don't see anything similar to that in Common Core Standards, but it's still in our textbook.  So I will be muddling through this part of the chapter next week.  It's a tricky one.  My kids have a tough time with things that aren't concrete.  They also have a hard time consistently adding and subtracting.  We've also been struggling with remembering the signs to add and subtract.  I'm not exactly looking forward to this week's instruction, because I remember the past years of doing this part of the chapter.

I decided that this year I needed to create something to make it easier for my students to understand the concepts and hopefully the week won't be too painful for us all.

I made this cute Time Machine Addition and Subtraction mini-unit for my kids and I'm offering it as a freebie in my TPT store.  You can click on the pic to download it.

Basically it works like this, you give the students a rule (use a highlighter to write on your mat if you're at home) and some counters (or pennies if at home).  Then tell them how many counters they need to put in the machine.  They then record how many went in and how many would come out.

If your students need it to be even more concrete, you can use counters for the number going in and the rule.  

You can also use this for subtraction.

Is anyone else required to teach this?  Do you think this would be useful to you?  The Time Machine Addition and Subtraction mini-unit comes with the work mat, the in/out recording sheet, 32 task cards with recording sheet and answer key, and 2 worksheets with answer key that could be used for assessment or practice.  If you can use this in your classroom, I'd love if you would leave some feedback!