[rzzzt]

There were some exercises in our high school physics textbook which required you to simplify a fraction by assuming pi^2 = g.

[semi-extrinsic]

Another nice one is that there's pi*10^7 seconds in a year. Which is accurate to three decimal places.

[pklausler]

"pi seconds are a nanocentury" is attributed to Adm. Grace Murray Hopper and it's surprisingly useful to know.