I was astonished when i calculated
I learned different in school. Yes, it's true, i could have calculated in my head. But i was lazy...
Calculator Version 2.3.4 i used.
Same error with OTA3.
Please open an issue at https://github.com/ubports/ubuntu-touch/issues about the problem. The forum is not an issue tracker, so reporting problems here is not especially helpful.
Seems to be fixed now: 49.8-2.1=47.7!
When you would read a bit about this problem, it would be more clear to you: In contrast to integer numbers floating point numbers can almost never calculated precisely on any CPU / computer on the market.
If you are interested please read e.g. https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html - Its a bit inclined but explains a lot.
Bottom line, what you learned in school is right, and the CPU lied to you. Unfortunately it did not round the number so to hide the lie
We fixed it by updating math.js from a 2015 version to 2018. 3 years pass and the lie seems to be perfect now
Thanks a lot for fixing this! Although it's just a funny small problem, fixing this tiny bugs also lead to a better system.
If i compare UT today with 1 or 2 years ago it improved really a lot! Stability, features and speed!