I have to calculate a combined score based on other scores i.e. s1, s2, s3, and s4.
For s1 and s2 the higher the number the better.
But for s3, it could be 0,1,2,3,4,5. But for s3 the higher the number it is worse i.e. 0 is the best and 5 is the worst.
And for s4 it could be from 0 to 500. But for s3 the higher the number it is worse.
So how to combine the scores?
Just to multiply
combined_score = s1 * s2 * s3 * s4 would not work.
As for s3 and s4 the higher the number is not always better. How to handle this case?
If the scales are linear and have the same weight, you need to transform all the scores to a common scale, then just add them together. Say one of the scores is $s$, on a scale from $s_w$ (worst score) to $s_b$ (best score). Note that the numerical value of $s_w$ can be greater than $s_b$. Then the scaled value $$s_s=\frac{s-s_w}{s_b-s_w}$$ This formula transforms all scores into scaled scores, where $0$ is the worst and $1$ is the best. So for you example in s3, $$s_{3s}=\frac{s_3-5}{1-5}=\frac{5-s_3}4$$ For s4 (assuming 500 is the worst score), then $$s_{4s}=\frac{s_4-500}{0-500}=1-\frac{s_4}{500}$$