Can anyone tell me what is recommended by the rules when rounding a score? Up or down? i.e. Creo (4) + Aquam (7) in the case of exhausting Spontaneous Magic is 11/2 = 5 or 11/2=6? I see that Aging is fixed to rounding up by the rules, but can't find a statement for spells. I use the rulebook in french, so it might be more obvious in english and lost in the process of translation.
IIRC you round up in all cases except ability and art xp progressions. Always choose the smallest integer larger than your fraction.
The default is that you do NOT round at all, but use the fractional result - except where you are explicitly told to .round in a certain direction.
In your example with fatiguing spontaneous magic the result would be 11/2 = 5.5. Enough for a level 5 spell, not enough for a level 6 spell.
Tanks, it's even clearer this way.
Note that what you are proposing is no different from rounding down, at least in the example that you are proposing.
The end result is no different, the method of reaching it is.
In other cases the end result would be equivalent to rounding up.
I'm not sure if ErikT's reading is correct, but his proposal would be sunstantially different from rounding down in terms of penetration. After all, 0 MR does resist against a spell with 0 penetration, but would be bypassed by a spell with 0.5 penetration.
Me neither. Personally I prefer to play with mathematical/conventional rounding. I.e. from .5 and above rounds up, anything below rounds down.
This has the advantage that it makes ArM rounding the same as normal rounding, which avoids having to deal with learning a whole new system of rounding just to be able to play the game.
Being both mathematical and conventional of mind, I think it is obvious that you do not round at all, unless the rules explicitly says so. Fractions pose no problem, neither mathematically nor conventionally.
It makes Spontaneous magic, which is not rounded by RaW, much easier.
I suspect this "no rounding for spontaneous magic" might just be a 5th ed. thing. I'll make a point of checking next time I've got my 4th core book out, though.
It isn't. In 4ed it says what to add up, to divide, and then the final result is the level cast. No mention of rounding.