Common Core, Inc.
Multi-Digit Whole Number Subtraction
A thorough exploration into subtracting multi-digit numbers, this series of lessons is an excellent way to guide learners of any skill level. With a step-by-step lesson plan and straightforward assessment tools, kids are sure to...
Arizona Department of Education
Area and Perimeter of Regular and Irregular Polygons
Extend young mathematicians' understanding of area with a geometry lesson on trapezoids. Building on their prior knowledge of rectangles and triangles, students learn how to calculate the area of trapezoids and other...
Lawrence Hall of Science
The Math Page: Skill in Arithmetic: The Meaning of Subtraction, and Mental Calculation
This website explains and defines basic subtraction. There are practice problems at the very end of this lesson.