Results Slide - taking one of two quizzes and reporting 100%

I have two quizzes in my module - depending on which group the user belongs to depends on which quiz they take, they must only take one.

I put each quiz in its own scene and have a results slide at the end - Quiz 1 has 12 questions quiz 2 has 14.

As far as I understand, I can't tell storyline to submit the results of "either one slide or the other" depending on which one has a score so I think what I'm meant to do is create a combined results slide which will be the one that reports back to my LMS?

My problem with this is,  if they score 12/12 on quiz 1, I want the report back to be 100% .. but I can only see combining the scores of the two results which gives an inaccurate percentage - is this possible? Forgive my newbieness!

Thanks :)