Pi X 5 = 15.7. Pi is equal to 3.14 then you multiply it by 5.
Circumference is 2 times pi times radius, so the circumference of this circle is 2 times pi times 5, or 10 times pi. If a decimal answer is needed, pi is approximately 3.14, so C=31.4
No, it is not.
15.7
3.141592654 * 5 = 15.70796327
The formula for a circumference is 2 times Pi times Radius. A diameter is twice the Radius, so the circumference is Diameter times Pi. 5 times Pi (3.14159) is approximately 15.70795. Pi has an endless number of digits to the right of the decimal point, so the best we can do is approximate.
15.072
The area of a circle is equal to pi times the radius squared. So in your case it would be 5 squared, (25) times pi which is equal to ~78.5
mass of proton is 6 x pi raised to power 5 times mass of electron
it is impossible to know because no one has been able to find the last digit of pi yet 5 times pi is 15.708 to 3 decimal places.
equivalent
I don't think there is such thing as 5 pied. Unless you mean "5 times pi", then the answer is yes. 'PI' and any multiple of it are irrational numbers.