This activity the kids love because they are able to check their work immediately. The first page is the worksheet that you give to them. They write their work in the boxes, then find their answer in the peices that you cut out in advance. The 2nd page of the document is 2 sets of the answers. Columns 1 and 2 go together and 3 and 4 go together. I would copy the 2nd page on construction paper (laminate if possible) and cut out for them before you pass them out.
It is a great way to practice this skill because you do not always have to tell the students, "yes, that is right." By having peices with the answers in front of them, they will know right away if they did it correctly.
Students feel like they are playing a game, but they are just practicing.