Here is an activity to use with elementary students of any age that helps build number sense. For any given grade level (or level of individual achievement) just choose a target that is appropriate for the student(s). It is great to do the activity on a repeating basis (i.e., once a week for a while) – just change out the pairs for the particular target each time.
Compatible Pairs: to 10. 50, 100, etc. Target: K-6
Write numbers on the chalkboard or prepare a transparency for the overhead. Include 5 or 6 pairs of numbers (mixed up in presentation) that will add to a target goal. Students write the numbers in compatible pairs as they see them.
When sharing the answers, ask students what strategies they used to find the pairs.
The difficulty of this exercise depends on the target sum as well as the similarity of the numbers given. Here are some suggestions for target numbers as well as some suggestions for number pairs.
I hope you will try this activity with your class soon!