Backing into Formula

This is a formula that is accurately being used in my spreadsheet. I did not create the formula but I am trying to "understand" what it is saying in the event I need to change it or edit it in the future. I have tried reading the formula and backing into it but I do not see how it's coming up with the answers. AS background, columns G4-BA4 assigned a percentage to the answeres in the columns below. The percentage adds up to 100 or 1.00. Columns G5:BA5 and below contain answers 1, 0, or NA. Hope this is enough to answer my question. Basically, if an answer is 0, the answer is wrong and it subtracts from 100% and based on the percentage that answer was given will result in a percentage correct. In example, if the question that they got wrong or "0" had 5% percentage points assigned, this formula returns back a 95%. AGain, I've tried backing into this but even though I know it works, I can't seem to get it to work in my own head. Just curious---

=sumproduct((g5:ba5=1)*($g$4:$BA$4))/(sumproduct(g5:ba5=1)*$g$4:$ba$4))+sumproduct((g5:ba5=0)*($g$4:$ba$4)))