Children add and subtract 100 to a number by focusing on the digit in its hundreds place. They add one more to the hundreds digit to mentally add 100 and take away one to mentally subtract 100.

This PowerPoint lesson is a multi-click animation sequence that introduces standards-based math skills and concepts. Also includes three practice pages at levels A (below grade level), B (at grade level), and C (above grade level), which may be distributed according to students' abilities