I have been using an idea from Warren Esty's excellent Precalculus (4th Edition) in class that is working very nicely. I have been having the Geometry students work through some tricky area problems. I'm more interested in their process than "the answer", and I told them as much. So I asked them to find their answers to the nearest tenth, write down how they got them, and then gave them this:
...which did wonders to relieve their anxiety, and took the emphasis off the answer, and put it on the process.