### 2nd Grade Subtraction Animations

Second graders in Ms. Gardner’s class at Holladay Elementary have been learning the difficult concept of subtracting with regrouping (SOL2.7). Sometimes abstract ideas become clearer when we can visualize them with an animation. It’s even better if we have someone verbally explaining the animation. The best way is to create and explain the animation yourself! So that’s what we did today using Keynote. First we opened up a blank Keynote and I showed them how to add a Title and change the theme. Next, I instructed the students to come up with two numbers less than 99 that would require regrouping to subtract. They added those numbers to their slide with text boxes. Then they used the shapes tool to represent the top number as base-10 blocks (bars for tens and cubes for ones). Now it was time to add the animations. This is where Ms. Gardner and I really got to see which students understood the concept and which ones didn’t. The used the Inspector to add “Build Out” or “Build In” animations to the different bars and cubes. They had to make one ten disappear and ten ones reappear. Next they had to make the correct number of ones and tens disappear to show the subtraction problem. At the end they should have had the same number of base-10 blocks as their answer. They used a text box to make their answer appear, and finally they recorded the voiceovers explaining each step. The students exported their slideshows as a QuickTime video. It was a lot of work for these second graders and took us a couple of days, but they hopefully they have a better understanding of subtraction with regrouping. You can see a couple of student examples here: Giada and Jessie.