First Grade Math Warm-Ups: Week of May 4-May 8, 2015

I had thoughts all last week of how I couldn’t wait until the Warm-Ups post to brag on the awesomeness that happened, but alas, I guess I saved it anyway….so get ready, this is definitely NOT first grade math happening here, people!

We had three problems this week, and they were all in the same vein–2-digit subtraction where kiddos were asked to try ALL 4 STRATEGIES we’ve worked on in our class this year.  And they were up to the challenge, even though it had been a while since we’d worked on subtraction.  I was SUPER impressed, and I think they were, too!

The benchmark in 1st grade says that only have to be able to subtract to 20, but since we were doing addition to 100, we went ahead and followed along with subtraction as well (why stop them if they can go farther??).  They also only had to be able to do it in 2 ways, but again, I think it’s good to be flexible with strategy and begin (even as a first grader) to learn which strategy is best for the numbers.  In this case we used each strategy each time, but talked about which ones made the most sense.  Let me show you the part we were most proud of:

IMG_3072I don’t know if you can tell, but that’s not an ordinary 2-digit subtraction problem.  Nope–it’s one that will need to use what we used to called regrouping but that honestly now we don’t really call anything.  It’s just what you do to make the problem work!  Please also notice that there’s no “stacking” or traditional algorithms here and these littles can still figure out the solution.  Nice, right?  I know some wouldn’t believe it’s possible….:)

My favorite part is when we started with sticks and dots, and we realized that we couldn’t do what the numbers told us to do–we couldn’t take 7 dots away from the 5 we had drawn.  Millie noticed it right away and then we had a great conversation about what we could do about that.  Makayla suggested that actually there were 10 dots inside each of the sticks we drew (how’s that place value work for ya?). We decided if we crossed off that last stick (which represents a 10) and added those 10 dots instead to the dots already there, then we could do it.  We ended up with 15 dots (ones) that we could take 7 away from.  We used the double-minus-1 problem of 14-7 is 7 so 15-7 is 8 to get that part of our answer.

Then, when we tried to do the same problem with splitting, we ran into the same problem–we didn’t enough to do that part of our problem.  Since we had just done it, we knew we could try it again, and moved the 10 from our 90 to make 80 and then the 5 became 15.  Voila!  It all worked out. 🙂

This is some pretty amazing stuff, and I’m impressed to hear both their fearlessness and pride when they figure out what to do.  I also love how differently 1st graders seem to tackle problems like this that are hard, or challenging, or that don’t at first seem like they’ll work–they just jump in and try something and see what happens.  They haven’t yet learned that they can’t do it, they aren’t worried about whether or not they make a mistake, they know they have many tools in their toolboxes that they can use till they figure it out.  I hope to be able to encourage this kind of approach to problem solving as I work with them again next year—crossing my fingers that I can help them keep that mindset for longer than maybe they would have…there’s hope at least. 🙂

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