# Question: degree of freedom analysis question the above textbook solution states...

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Degree of Freedom Analysis question

The above textbook solution states that there are 3 unknown species (n1, n2, n3), and 2 balances (one for propane, and one for air). This yields a degree of freedom of 1.

However, couldn`t we add an "overall system" equation? (n1+n2 = n3)? this would give us a 3rd equation, and make our DOF of zero.

Is this allowed? If not, could some one please explain in detail why not?