Understand the meaning of the equal sign, and determine if equations involving addition and subtraction are true or false. CCSSM 1.OA.7
That’s right, understanding the true meaning of the equal sign–it does not mean ‘the answer is coming’–is a 1st grade common core standard. See this blog post for more about the 1st grade standard. But what about your 3rd graders? Or 4th or 5th graders? That standard wasn’t around when they were in 1st grade. I made this little activity for my 5th Grade/3rd Grade peer tutoring group, and I introduced it by just showing them the green strip (no dominoes) and asking what the equal sign means. The most common response was (very confidentally, I might add) that we would “add the first two numbers to get an answer and then add the last number on.” Not surprising. Also not right.
I explained to the kids that the equal sign is like a balance, and then I held out my arms to the side with my flat palms facing up to illustrate. I told them that it simply means that whatever is on one side of the balance has to equal what’s on the other side.
If I have 3 + 2 on this side, how much is the side worth? Five. Right! So if I have 3 + 2 on this side and 4 on the other side, do they balance? No. (I showed with my arms how the 5 side would be ‘heavier’) So what would we have to add to the 4 side to make the two sides balance? One! So, if I have 2 + 3 on this side and 4 + 1 on the other side, they balance? Yes. How do you know? Because 2 + 3 is 5 and 4 + 1 is 5. Oh! Good thinking.
We did a few more examples like that with one digit numbers, and then I introduced the activity pictured below. It was actually one of my 5th grade tutors who realized she could place the green strip at the top of the paper and put the computation underneath (way to go, Skylar!). Then you just move the strip down the paper as you do additional problems (see the second picture). The dominoes are used to make 2-digit numbers, and the empty space can move around. Notice that underneath we practiced some of the alternate strategies the kids are learning in their number talks.
It was really cute watching the 5th graders teach their 3rd grade tutees this very difficult concept. Grab your copy of the mat here. I’d love to hear your comments!