I used "My Crazy Friend" for the first time in my classroom last week. "My Crazy Friend" is a teaching technique that allows the teacher to introduce a new idea or method of solving a certain type of problem without becoming the one and only authority in the classroom. It also allows students to consider the idea from My Crazy Friend along with other ideas that are generated by students in the classroom. I asked the students how to convert 2/3 into a percent. Here is a list of ideas solutions that they came up with: 66.7%, 67%, 66.6%, 66.67% and 66.66% (repeating). No one in the class came up with 66 2/3%. So I said, I have this crazy friend who says that one way to convert fractions into decimals is to multiply the fraction by 100%. The students tried it and there were some exclamations of surprise when they realized that this gave them the percent in mixed number form. We then spent some time discussing why and how this method works and one student contributed to the discussion by explaining that since 100% = 1, multiplying by 100% does not change the value of the fraction.
Here is a graphic organizer that I use to summarize how to convert from fraction to percent and from decimals to percents using this method. It also shows the opposite--converting to fractions and decimals from percents by dividing by 100. I print this out on a half sheet of paper and the students tape it into their math journals for reference.