As a First Grade teacher, I have found that it is difficult to find simple fluency tests for my students with a little added touch of personality. So, I decided to make my own. I also think that 20 problems is the perfect amount for us at the beginning of the year.
When we start these sheets, I actually compete with my students just for fun. The goal is to finish the 20 problems within about 2 minutes. After we have done all of the addition sheets, we will go back through and try to finish within 1 minute. Depending on the students, I base the testing upon their needs. Even with Common Core in place, we are still expected to make sure our students are fluent with their math facts. So, this is just a tool to help them along the way. The goal by the end of the year is for them to complete a sheet within 45 seconds. That prepares them for the 2nd grade goal of completing 30 problems in 1 minute and 15 seconds.