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You can also use  π = 4 arctan(1) (where arctan is ""tan-1""), i.e. type ""1"", ""tan-1"" (in RAD mode), and multiply by 4.
However, knowing kids, I find it somehow suspicious that you say ""very young"" and ""I'm about 10 years old"" - usually kids of that age are very precise concerning their age... — Talk "