Combining flours with different ratios of protein to achieve a specific result

Question

This is an actual problem I am trying to solve while baking!

flour x contains 12.7% protein

flour y contains 80% protein

how much of each flour do you need to get 272g of flour with 14.2% protein?

I eventually was able to figure it out by plugging in numbers but I want to know how to formulate it as an algebra problem.

Answer 1

Let x = 12.7% flour and y = 80% flour

x + y = 272

.127x + .8y = .142*272

x = 272 - y

Substitute

.127(272-y) + .8y = .142*272

If you work through the arithmetic, you will get a value for x and use it to get y.

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