Estimating PI without a calculator

[davetheguru]

Or if you just have a 4 function simple one...
An reasonably accurate estimate can be done by taking the sequence:
1 1 3 3 5 5
and putting the old division box /---- in the middle (sorry for the poor drawing but this way helps remember to process for some) so that you have:
____
113 / 355 or rather,

355
----
113

to get something like:
3.14159292035 (on my HP50)