This is a quick and easy way to get kids working with numbers and operations each day.
The idea is that you have a number each day, and that number is the day's magic number. You may choose to write down each number on a slip of paper, starting with one and ending with the number of school days you have, and draw one each day, or you can use something like the calender day, or ask you students to choose one.
Once you have your number selected, ask your students to write down a equation using that number. The possibilities are endless with this and you will need to vary this according to the ages and abilities of your students. It can be anything from make it the solution to your equation, to include as a number in your equations. You may also choose to specify the type of operation to be used, as well as how many they need to use.
Once your students have turned in their slips of paper (nameless), select a few slips to read aloud to the class and let your class have a few seconds to mill over the answer in their heads and then answer "yes or no" to whether or not the equation worked or to determine the answer.
The idea isn't to test your students to their abilities to write and solve equations using specified numbers and operations, but instead to allow for mental math practice in a quick and easy way.
This activity could be something that is implemented into the daily routine or just simply done as a special activity or a filler. The idea is, once you students understand how it works, it should not take up more than 10-15 minutes of your day.
The Homeschooler's Hack - Don't have a class of 31 excited second graders? Instead do you have a 4th grader, 1st grader, and a preschooler? You can still make this work! Have your preschooler practice counting to the number, and then count out that many number chips. Have your 1st grader work with addition, which your 4th grader works with multiplication. Have your 4th grader write problems for your 1st grader to solve. Write some problems your self, making some wrong, and let your child correct you (they love that!). The possibilities are endless! The idea is it's a quick activity, and everyone is working with the same number, even if it's different ways.