“Can you solve 8+7 mentally?” I say to my class on Friday morning. I knew they could do this one easily but I really wanted to know… “How did you do it?”
“I looked for the friendly number of 10. So thought of it as 10+5 and got 15,” one child said.
Another student shared “I know the doubles fact 7+7 is 14 and then I added 1 more to get 15.”
This is all part of a number string conversation that our math specialist has been promoting this year. It is getting students to think and discuss the how of their math thinking and to be flexible with their thinking about numbers.
“How about 28+77?” I venture. Their thinking and discussing of this problem was really deep so I tried 1 more…
“What about 428+177,” I ask. The students share some really incredible strategies, some of which really surprise me. They are getting so good at these.
“I am blown away by your thinking,” I say. “There is no way when I was in 2nd grade that I would be able to solve this math in my head.”
“Really? You’re kidding us,” comes the chorus of kids. “They’re so easy.”
“It’s true! I didn’t even learn multiplication (our previous unit) until 3rd grade,” I tell them.
“No way! You could definitely do what we just did.”
“Nope!” I exclaim.
“You’re 2nd grade teacher must not have been too good then!” says a quiet voice from the cluster that then turns in to a bunch of heads being nodded and words of agreement.
I smile! If only they knew what elementary school was like back then AND what a compliment that was.
Standing Tall 
LOVE this slice. I work so closely with the math coach and she would be ecstatic with the mental math fun your class is having. Those kiddos are lucky to have you!
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Great story! Every day kids come up with amazing stuff. I too love hearing kids share their math thinking.
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I can totally hear that one quiet voice speaking aloud what the others are thinking! Great Slice!
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I, too, am blown away by these strategies from second graders. I love the conversations and the sharing participation. Feel good about both, and bask in the compliment!
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I learned so much from this post. I’ve never heard of a “friendly number” and still can’t do the big adding in my head like your students. Now I want to learn.
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I need my 6th graders to come to you! My co-teacher and I talk all the time about how our kids DON’T do mental math. They don’t use these strategies and are amazed that my co-teacher and I can do all kinds of math operations in our heads. And when we explain how we look for patterns and use what we know when the numbers get larger, they look at us like deer in headlights! They need to go back a couple years and relearn some of this math. We have been using a number strings book to try to work on some of this mental math that your 2nd graders would probably love!
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Good for you! This is a great math conversation that you are having with your second graders. It is also a great reminder of how different school is now versus in the past. Like joyousthoughts wrote, my sixth graders also need some help with mental math. Thanks for sharing!
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-It’s all about perspective, isn’t it?! You’re right about how much things have changed and how much more challenging things are for today’s students. I’ll just say this: I learned how to calculate 15% in a hot minute, when I started waiting tables …
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I wish I had been a student in your class! I would be a different adult….in my mathematical understandings.
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From the mouth of babes. We have learned so much about teaching mental math.
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