My 9th grade physics students were taught a method for solving speed problems in middle school that does not require algebra. The variables are separated in a diagram of a triangle (or a circle). When you cover up the variable you are solving for, the diagram shows you the recipe on how to solve the problem. If you're not familiar with what I'm talking about, here's a link to an example using Ohm's Law: http://www.electronics-tutorials.ws/dccircuits/dcp_2.html
I have avoided use of this device for a variety of reasons. First of all, it has zero meaning. I feel that it is important to reinforce my students' algebra skills, which this method completely skips. I also prefer Hewitt's method on using equations as "guides to thinking" which these triangles/circles avoid. Finally, I have found in the past that various memory devices in math (e.g. FOIL, cross multiplication, etc.) have limited function and students tend to use them incorrectly much of the time.
However, I am wondering if I should reconsider my stubborn position. I have had many students approach me this year showing me the triangle and claiming "here's an easier way to solve the problems!" In addition, at the NSTA conference I was introduced to a text entitled "Active Physics" by Arthur Eisenkraft which uses the circle for every equation given in the book.
Again, these are 9th graders I am teaching, so maybe I should not be such a stickler on going through all the algebra. This device is primarily used for "plug and chug" problems anyway, which have little meaning themselves.
Do any of you use this method with your students? Have you found it useful? Do you have any tips to make it more meaningful and universal? Do you see it as a hindrance?
Thanks in advance for your collective knowledge and wisdom!