Quick Question on Uncertainty of PI

[circuscircus]

Homework Statement

http://img413.imageshack.us/img413/226/8m1celf4.gif

On b, why is the pi exp 3.18 +- 0.04 and not .012?

Homework Equations

The Attempt at a Solution

 

[D H]

The 0.012 arises from $\Delta\pi/\pi = 0.012$. In other words, it is a relative error. Clearing the fraction gves the absolute error: $\Delta\pi = 0.012\pi\approx0.04$