NLVM : percentages

This week I was playing with the Percentages found in Number and Operations in Pre K-2. I like this manipulative because I know that students still have a problem with percentages even at the high school level. The good thing about this is that it lets you input the values yourself. For example, you can put in the whole, the part and it will compute the percentage for you. You can also work backwards, where you can input the percentage, the part and it will compute the whole. The equation that is use is a ratio and proportion equation. Part over the whole equals the percentage over a 100%. If you try to input a part that is greater than the whole, it will tell you that the part needs to be less than the whole. That way the students will understand that while working with numbers where the maximum is a 100 percent, the part can not be bigger than the whole. It would be a good intro to the possibility of having numbers over a 100 percent.