The recipe is

320g starter dough

450g water

800g flour

If I want a larger mix, and I have 500g of the starter dough, i can easily work out the proportion of other ingredients, by dividing 500g by 320g (1.56), then multiplying the result by 450g (=703g) for water and by 800g (=1250g) for the flour.

I like the way these numbers work out precisely the amount I need. I'm trying to work out something else, now I feel so smart. How do I manipulate these numbers to give me a combined weight of exactly 3000g , whilst still maintaining the proportions? Can you help me out please?