r/MathHelp • u/baadbettyy • 1d ago

Sourdough Hydration help

I’d like to better understand baker’s percentages. Haven’t been in math for a few years. Couple decades. So a bit rusty. I was going to plug into a free calculator but found this sub for help and I’d like a step by step just so I can perhaps figure out future recipes on my own.

So. The equation=

Total hydration % = (total flour/total water) x 100

The part I’m having trouble with is that sourdough starter is made of flour and water and for precision should be considered in the math.

So,

67=(1000/x+50)x100 is the formula I can up with and I’m not even sure if I did that right.

I’d like a 67% hydration with 1000 grams of flour total and 100 grams of starter. The starter would be 50 grams each water/flour.

So now I thought I would just have to solve for x?

Also need help solving for x.

Sorry if this is so juvenile. I would like to just understand. Thanks for anyone’s help.

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u/edderiofer 1d ago

67=(1000/x+50)x100 is the formula I can up with and I’m not even sure if I did that right.

Perhaps you should first explain what "x" represents. I can see that in your attempt, the 67 represents your desired hydration percentage, the 1000 represents the total amount of flour, and the 50 represents the amount of water in your starter, but it's not clear to me what quantity "x" represents here.

Once you pin down what unknown quantity you're looking for, then you can figure out where in the formula it should go.

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u/baadbettyy 1d ago

Oh duh…

The rest of the water i would need for the recipe. So x + 50 would = total water for the recipe? I think

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u/edderiofer 1d ago

So, x represents the amount of water you're adding to your 1000 grams of flour and 100 grams of starter (which itself contains 50 grams of flour and 50 grams of water). OK.

How much total flour is there in this mixture of water, flour, and starter?

How much total water is there in this mixture of water, flour, and starter?

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u/baadbettyy 1d ago

Total flour is 1000g from 50g starter + 950 added
Total water is 50g starter + unknown added

? Is that what you’re asking?

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u/edderiofer 1d ago

Yep. So, we can now be sure that your equation is correct. (With one small correction: You should write your fraction as "1000/(x+50)" rather than "1000/x+50"; the latter is interpreted as (1000/x) + 50, which is a very different thing.)

Now, to the matter of solving your equation. You have a number of things that you are doing to your unknown x:

  • First, you are adding 50 to x.

  • Then, you are dividing 1000 by the result of this first step.

  • Finally, you are multiplying the result of the second step by 100, and ending up with 67.

Focus only on the very last step for now. Given that the result of your third step was 67, can you figure out what the result of your second step was?