>nor is your hand calculator a computer, is it?<

Yes it is. Just a very weak one.

I tried on the windows calculator and it took about 1 second to give me an answer.

The quantile of 0.05 for binomilal(0.2,10000) is 1934.

Thats roughtly 1934 seconds of waiting which is a fair amount of time (about 30 minutes).

With 100 000!, I gave up after 30 seconds of waiting.

The time factor increases very quickly.