''For large values of three, and small values of pi.''

If you don't need the accuracy (was that temperature 12 000 000 C or 12 000 000 K?), and can get away with an approximation to an OrderOfMagnitude, '''pi = 3''' and '''pi^2 = 10'''. 

Or rather pi^2 = g; cancels out nicely in physics courses. ''But for such approximations, g also equals 10. :-)''

See also ValueOfPi

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''"The value of 'pi', recited to the length of one decimal digit...''
    "3".
''There.  That's it.   ;->''