Most of our kids are pretty proficient at knowing how to follow the step-by-step procedure of adding and subtracting multi-digit numbers. But I really want our students to understand what's really happening to the numbers and why it's happening. For example, when subtracting multi-digit numbers - many kids can tell you, "You cross out the 3 and make it a 2. Then you turn the 4 into a 14." But when you ask them, "Why? Why does that happen? Why does the 3 become a 2? Why does the 4 become a 14?" - many kids are at a complete loss. So this week we have used base ten blocks to demonstrate our understanding of what happens when we add and subtract. These hands-on lessons have really made an impact on our kids. Several students have told me, "Wow, I never knew that's what really happened," or "I kinda knew what was happening, but now I really get it." I love watching the A-ha's on their faces when they come to these new understandings!
This is a drawing from Richie's math notebook. He's drawn a picture to explain how 277 + 58 = 335. Notice how he groups the ones together to make a ten, then moves the ten over with the other tens. Then he groups 10 tens together to make a 100, and then moves that one hundred over with the other hundred.
This is a drawing from Emma's math notebook, where she is explaining what happens when you subtract 158 from 243. Notice how she takes a ten and moves it over to the ones, creating 13 ones. Then she moves a 100 over to the tens, creating 13 tens.
Nakia and Porter are using the base ten blocks to demonstrate their understanding of addition and subtraction.
Wednesday, September 24, 2008
Addition and Subtraction
Subscribe to:
Post Comments (Atom)
3 comments:
I love the math drawings, never seen anything like that done before. Whatever works. But doesn't it take a looong time? Or, is the goal to get the kids to conceptualize this way and then they go back to doing the "old-school" way? -Kathleen Moore
You've got it - the goal is for kids to conceptualize what's happening with the numbers (or symbols). I want the kids to connect what's happening with the base ten blocks to what they do on paper. When they cross out a "7" and make it a "6," what's actually happening? The base ten blocks allow us to see why the "old-school" way actually works.
This is a wonderful classroom blog! I am very impressed by all the great work that is going on in your class. My students thought that your class might enjoy our classroom blog - jmundorf.edublogs.org. We are a fifth grade class on Marco Island in Southwest Florida. Enjoy!
Post a Comment