If it's really fancy, like with custard inside and whipped cream on top, it might cost as much as $10 depending on where you buy it.
If you're talking about the greek letter 'pi' ( π ) that's used in math, then there's no exact answer, because the exact value of that number can never be written on paper with digits.
It starts out with 3.14159 26535 89792 and it just keeps going and never ends.
If you need to work with pi in a math problem, then your answer can never be exactly exact, but you can get as close to it as you want to by using more digits in the decimal. 3.14 is usually good enough, but supercomputers have been used to calculate something like 4 trillion digits of pi after the decimal point, and it still never ends !
If you use either 3.14 or ' 22 / 7 ' for pi, then your answer is only about 0.05% wrong, and that's pretty good !
