HP 32S II fraction issue

[cjsuk]

Hi all. Just discovered a footgun, not really a bug as such, in the HP 32S II.

When you enter a fraction 1/2 then 1/3 then subtract it'll give you 1/5 as the answer rather than 1/6. I was being lazy and didn't notice this half way through a calculation and shot myself in the foot on something. Doh.

Well investigating it appears that the denominator in FDISP is reduced in some way from 1/(0.5-0.333...). This is 5.999... which it rounds down to 5 as the denominator rather than 6. Grr.

That'll teach me to trust and not verify!