1. The problem statement, all variables and given/known data Given three spring scale readings, positioned at unknown angles, find the mass of the weight hanging from all three scales without using trig, and without measuring the angles. You have only a yard stick. This is a static equilibrium problem. 2. Relevant equations Not allowed to use trig. Can only use a^2+b^2=c^2. 3. The attempt at a solution I assume I have to measure vertical and horizontal components by hand, as I am not allowed to take an angular reading. What I don't understand is how do I take a reading without some known level plane, other than the floor, and without a level also attached to my yardstick? If I had a level plane, at or around the top of the weight, I could measure <x,y,z> displacement. The experiment gives hints that we're supposed to somehow use Similar Triangles, and that the vector components make right triangles. Obviously vector components would make right triangles if I could measure angles and use trig to get those components, but I'm told not to use trig. One image shows the apparatus pushed up against a white board. If I can't use trig, how does that help me in a 3 spring scale setup? I don't get it at all. I want to just remove the weight and place it on a scale.... I know I must calculate the opposing force using the vectors by summing their component parts. But how do I accurately get the component parts with only knowing the readings on the scales?