I don't want to turn math into a touchy-feely all-answers-are-right-answers nonsense subject, but estimation is a good skill in math, engineering, and computing

I don't want to turn math into a touchy-feely all-answers-are-right-answers nonsense subject, but estimation is a good skill in math, engineering, and computing. Two examples: Fermi problems[1] and Jon Bentley's "back of the envelope"[2] estimates. [1] http://en.wikipedia.org/wiki/Fermi_problem http://en.wikipedia.org/wiki/Fermi_problem [2] http://www.csie.fju.edu.tw/~yeh/research/papers/os-reading-list/bentley-cacm84-envelope.pdf http://www.csie.fju.edu.tw/~yeh/research/papers/os-reading-l... and http://www.eecs.harvard.edu/cs261/background/p176-bentley.pdf http://www.eecs.harvard.edu/cs261/background/p176-bentley.pd...