# Calculate new average from two other averages with its respective totals/counts

I have the next film named Blade Runner and it has two version (director cut and theatrical cut) and I rate the director cut with a 7 and the theatrical cut with a 8, so the average would be:

(7 + 8) / 2 = 7.5

I have another average of all films (the 7 and 8 scores are of blade runner, the 9 and 10 scores are from other films) as below:

(7 + 8 + 9 + 10) / 4 = 8.5

Knowing ONLY the total of scores (2) and the average (7.5) (without the scores) of Blade Runner, I want remove it of the average of films (Also, knowing only its total scores (4) and average (8.5) of all films). Is Possible do it? Or I need to know the scores of all films to calculate the new average?

• So you want to know what the average is without the effect of the Blade Runner scores? If so, you need to also know how many Blade Runner versions are in there (actually there are five versions :P) – Bobson Dugnutt Mar 5 '16 at 17:09

Yes, I think it's possible based on my understanding of your question: $$\text{New average} = \frac{\underbrace{8.5 \times 4}_{\text{sum of all ratings}} - \underbrace{7.5 \times 2}_{\text{sum of Blade runner ratings}}}{\underbrace{4-2}_{\text{number of films without Blade Runner}}} = 9.5$$