This is a "dominos" like activity where students will choose a card to start on, set up and solve the proportion problem, find the answer on another card and then solve the problem on the same card that had their answer on it.
They continue this process until they have lined up all their cards like dominoes. This activity could also easily be completed using stations or a scavenger hunt type task depending on the needs of your classroom.
I usually have pairs complete this activity. Depending on the skill level of your class this can be a short review to assess retention or a concept development task. Time will vary based on skill level of students.
This file is a word document so it could be modified according to individual teacher needs, but if the formatting doesn't work for you, email me and I will send you a PDF version.