I have used this in my class as part of our review days before our test. I split the students up into groups of 4 (3 is OK, too). I give each group 2 chart markers and a large piece of chart paper. They are to work together to write out their complete, worked out solution to the two problems that their group receives.
They have about 20 minutes to complete this part of the activity.
Then the students will split up; two will remain with their poster while the other two proceed to go around the classroom, visiting every other group's poster. The two group members remaining are to act as the "teachers" and explain how to solve the problems. "Students" are allowed to ask questions, especially if they do not understand. They will rotate around the room until they have gone through all of the problems.
Once they return back to their own poster, they will switch places with the other two members of their group. The process repeats until everyone has had a chance to learn and master all of the problems!