>>11002544Unless you want the exact number down to 6 significant figures or so: the poor mans approximation goes like this:
You are looking for the number y, for which y^3^2 = z^2 = x. z is still somewhat easy to find: 25^2 is 625, 28^2 is 784, 27^2 is 729 (I need 12 seconds at most to calculate those numbers in my head, but it can go much faster with training). So z is 27 -- cubic root of 27 is trivial, 3, but your would do the same thing and plug and chuck numbers with 1 significant figure, find two reasonably close values, then increase the amount of significant figures until you are as close as you want and need it to. This is, by the way, a good training for your sense of magnitude to sanity check results a calculator may spit out.
