In afterschool tutoring, my second graders had been working hard on learning their doubles addition facts. I felt they had developed a pretty good understanding of these facts. Now, they were ready to move on to subtraction. I really wanted to make sure that my students understood that addition and subtraction are inverse operations.
We began by using manipulatives and our "Part-Part-Whole" Mat. I gave students an amount to make in the "whole" section. Then, students counted out the cubes evenly into each "Part" section. The "Part" sections had to have equal amounts of cubes. We came up with the subtraction number sentence to represent our problem. (Click the picture for a copy of the mat.)
Students were still able to use the manipulatives and mats to complete the next activity. Students picked a number, and together we determined what would be half of that total amount. Then, we came up with the corresponding number sentence.
To continue practicing, students played a game called "Halves Race." Students spun the spinner to get a subtraction half fact. Students solved the fact and then moved their game piece to the corresponding answer on the board.
What is one of your favorite math games to play with your students?