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[Kirian]

In all seriousness, though, when you're doing the initial math for things in engineering, using pi = 3 is kinda common.  Remember that up until the 1970s, engineers only worried about three significant digits... on their slide rules...

Maybe that's why in the 70s you could buy cars with two inch gaps around the door where it was supposed to meet the frame and it was considered fairly acceptable.

That would actually be inaccurate even at two significant digits.  Three SD is 1 ppm tolerance, or somewhere in the 1 mm range for a car door.

Remember, we sent twelve people to the surface of the moon using items that were engineered mostly with slide rules, though they did have computers available for some of the more difficult calculations.  (I understand they did build some much larger slide rules to get four or five 9s of precision for Apollo though.)

[WanderingWinder]

Eh, you can do logs to three sig figs in your head without too much difficulty.

The order of magnitude thing, well I don't know about that, I have always seen things reported with proper precision (i.e. sig fig rules with measurement uncertainty and whatnot), usually pretty precise. Though we do talk about orders of magnitude to get ballpark ideas of what stuff actually means?

My best guess though, is that it has something to do with what I got taught as the distinction between small numbers, large numbers, and very large numbers (in a thermo/statistical mechanics class):
You can add a small number to a large number and it doesn't make much difference.
You can multiply a very large number by a large number, and it doesn't make much difference.

[Tables]

The worrying thing is, I read all the way to the end without realising the thread had derailed.

In other news, we should switch to base 12. It's nicer for many branches of maths, in theory, or so I've heard.

[dondon151]

Too bad it is only intuitive to polydactyls...