Students may be able to set up a relevant proportion and solve through cross multiplication. However, this ability may not reflect the desired mathematical understanding of the covarying relationship that exists between two variables or the equivalent relationship that exists between two ratios. Students who lack this understanding are likely to use a proportion and the cross-multiplication algorithm to solve missing-value problems even when the quantities do not covary proportionally. The Cats and Rats problem is a rich example of how a table or proportion is not necessary to make sense of and solve a proportional situation. To solve the problem, students can visualize the context and reason about how changes to one variable will affect another variable. A table can serve as a tool for recording students' calculations, and the variety of approaches to the solution can be shared. (Contains 3 tables)