Greetings, I'm attending a grad school in the fall whose Ph.D. comprehensive exams place a *huge* emphasis on order of magnitude estimations and dimensional analysis problems. I'm much better at problems that involve a little more mathematical playfulness and theory; I'm a little worried about these other kinds of problems. Does anyone know of a good guide on the internet (or section of a book) that introduces techniques like these? I've tried looking but didn't find anything terribly promising. Thanks in advance!