A 120 chart is a great tool for supporting addition and subtraction with our younger kiddos, especially as they start to work with larger numbers. I would suggest having kids add and subtract using a 120 chart before teaching them any kind of formal computation. Here’s what I mean by that. Think of adding 34 + 28. Just looking at it, that would be considered a problem that requires regrouping. Using the traditional algorithm, you’d add the 4 ones to the 8 ones, getting 12 ones. You’d need to regroup 1 ten to the tens column. Pretty complicated!!
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Now, look at the 120 chart below and think of how you would use the 120 chart to solve 34 + 28. I’ll give you a minute…
Chances are, you used something similar to one of these methods:
- Start on the number 34. Count on 28 to get to 62.
- Start on the number 34. Jump down two rows to 54. Count on 8 more to get to 62.
- Start on the number 34. Jump down one ten to 44 and another ten to 54. Add 6 to get to 60. Add another 2 to get to 62.
- Start on the number 34. Jump down three rows to 64. Come back 2 to 62.
- Start on the number 34. Move ahead 6 o get to 40. Jump down two rows to get to 60. Move another 2 to get to 62.
- Start on the number 34. Count on 8 more to get to 42. Jump down two rows to get to 62.
If you have even a different way, I hope you’ll leave a comment and describe it. Are any of these ways wrong? NO! I would argue that counting on 28 is not efficient, but it’s not wrong. What’s important is that, just like I’ve done here, you let your kiddos share their strategies with the rest of the class. I would literally have them come up to a large 120 chart and point to what they did as they describe it. Hopefully, your friend who counts on 28 will find a new, more efficient strategy to try.
Click here to grab your own ghostly 120 chart. 🙂