## Basic math question... How to change the hydration in a starter?

OK, my mother starter is 100% hydration. For a recipe I am working on, I want to use a 70% hydration starter.

If I start with 150 grams of 100% starter, how do I build this to 450 grams of 70% hydration starter? The math escapes me. The problem is that the 70% figure isn't 70% of 450, but 70% of the total flour weight. However, how do I arrive at the total flour weight? It would seem a simple problem, but none of the figures I am coming up with work.

I know that 100% hydration starter is 50% flour and 50% water. A 70% hydration starter should be 42.8571% water (100/70). This doesn't work, however. Obviously, I am miscalculating.

**Understand that I am not asking what the total flour weight is in 450 grams of 70% hydration flour, but how to arrive at that figure.**

I would gladly do a search, but I have no idea how to word this in search terms.