November 17, 2008
Addition by subtraction
We just published a new elementary math Gizmo, called Subtracting Decimals (Base-10 Blocks). This Gizmo completes our suite of three Base-10 Blocks Gizmos--the others are Modeling Decimals (Base-10 Blocks) and Adding Decimals (Base-10 Blocks).
With these Gizmos, students will gain a deeper understanding of place value, the base-10 system, and regrouping during addition ("carrying") and subtraction ("borrowing"). Students will see that the rules for adding and subtracting decimals are no different from the rules for adding and subtracting whole numbers, and will see why it is necessary to line up the decimal points when adding or subtracting decimals.