Are Your Students Struggling with Learning Subtraction Regrouping?
Two years ago I was introduced to math number discs and began using them in my classroom. I have come to rely on teaching regrouping using the math number discs after modeling regrouping with base ten blocks on a mat. These number discs (which are really expensive to purchase) are marked with 1′s, 10′s, and 100′s. An inexpensive alternative to using the ready made number discs is buying colored bingo chips and writing numbers on these yourself. Every place value position is a different color. The ones are white, the tens are red, the hundreds are orange, and the thousands are yellow. Students group the discs to represent a number on their place value mats and then take away the needed discs. Moving the discs around on the mat themselves does not seem to help students make the connection as much as having them draw and mark out the discs as they subtract. When they notice there are no more discs to mark out in the tens place for example, students realize they have to borrow from the hundreds place, mark out a hundred disc, and draw ten tens discs. If you scaffold this understanding to the actual borrowing and show students that when you borrow from the hundreds place to bring over ten tens, students have a light bulb moment and see the connection to all the marking out and rewriting of numbers that occurs in the abstract algorithm we call subtraction with regrouping.
Also, I am including a link below to my July 14th post in which I am showcasing a Smart Board lesson and practice pages that I created using interactive number discs.
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