The other day I had an experience that I don't often have...I was teaching my students how to subtracting mixed numbers with renaming. (Example: 5 - 2 1/3 or 6 3/8 - 4 1/8). In these situations you have to borrow one from the whole number, and either create a fraction, or rename the fraction given in the top number in order to be able to subtract. I have a great flipchart that I found on Promethean Planet to teach this and we did several examples. I then had my students complete a few practice problems and noticed that they really were grasping this concept quickly. It went so fast that I was not prepared to have so much time at the end of class to fill.
I wished that I had a set of task cards or something to allow them to continue to get more practice and allow me to have something I could use to assess them, but I didn't! Then it dawned on me...the fastest way to find enough task cards for an entire class to work on is to have them create them themselves!
I passed out an index card to each student. They had to create a mixed number subtraction problem in which the top number was either a whole number, or a mixed number in which the fraction was smaller than the fraction on the bottom. They each wrote their class number in the top right corner, created their problem, and solved their problem on the back in order to create an answer key for their task card.