The equation tells me, and I have been tracking since my first 4 star. Since uber rounds to the nearest hundredth, I cam check if all non 5 stars are 4 or if one was a 3. So, 179 x 5 = 895, if 4 trips are 4 stars, then my total score would be 891, and 891 ÷ 179 = 4.97765~, which rounded up would be 4.98.
However, if 1 trip were 3 starred my total would have to be at least 890, and 890 ÷ 179 = 4.9720~, rounds to 4.97.
Yes, it will be convoluted at a certain point of so many trips, but I check it after every non 5 star rating to see the difference for now. Oh, and I like math a little if it didn't show