As I said in the previous message now that multichoice answers are used a lot in Formulas questions (just for history this feature was undocumented in Hon Wai Lau documentation, I discovered it when I studied the code ) I think they need a little more love to improve the display
I added some styling because the labels were too close from the radio buttons and i managed to have something similar both in Boost and More or Clean theme (this was NOT the easy part !)
But maybe you have already spotted some other change in the above screenshots? I added a numbering feature to the choices. I simply borrowed the one from the multichoice qtype (similar to what is doing calculated multichoice question type) to avoid the need to duplicate code.
So that means that the formulas qtype is now dependent of the multichoice qtype but as I think qtype_multichoice is installed on all Moodle websites this shouldn't be a problem for anyone.
I didn't bother to introduce a setting for the default value, the Formulas qtype simply use the one defined for the multichoice qtype.
I also introduced a new sigfig function (sigfig for significant figures) with two numerical arguments the first one is the float to be displayed and the second one is an integer : the desired number of significant figures. The function return a string ready to be displayed (it can't be a number as we need trailing zeros in some cases !)
I will post here when this version will be available in the Moodle plugin database