My old TI-36X Solar

This is the calculator that got me through junior high and high school. It even handles fractions, which is what you see on the display there.

355/113 is a very close approximation of PI, accurate to 6 decimal places.

Yes the calculator also has a proper constant for PI, but 355/113 is a pretty nifty trick in it of itself.

355/113 = 3.14159292, at least on this calculator.