title: Python handling formula differently than expected
body: <p>I'm creating a dive table for private use and I'm running into an error for calculating EAD</p>
  
  <pre><code>def calculate_ead(self):
      nitrogen = 100 - self.mix
      EAD = (self.depth + 10) * nitrogen / 0.79 - 10
      self.depth = int(EAD)
  </code></pre>
  
  <p>This calculation gives off an insanely high number (around thousands). I got the formula off of <a href="https://en.wikipedia.org/wiki/Equivalent_air_depth" rel="nofollow noreferrer">this</a> site and in the calculations in feet section. The calculation when the mix is above 21 should give off a lower number than the depth.</p>
  
  <p>My Initializing of depth and other things: </p>
  
  <pre><code>def __init__(self, d=35, t=30, m=21, p=1.6):
          self.depth = int(d)  # Depth
          self.time = int(t)  # Time
          self.mix = int(m)  # Mix (Oxygen integer)
          self.max_po2 = float(p)
  </code></pre>
  
  <p>Mix in this case in the percentage of oxygen so when a hundred is subtracted by it it should give the fraction of nitrogen for this formula EAD = (Depth + 10) × Fraction of N2 / 0.79 − 10</p>
  
  <p>Tell me what I'm doing wrong?
  Sample test from interactive shell:</p>
  
  <pre><code>depth = 90
  mix = 36
  nitrogen = 100 - mix
  EAD = (depth + 10) * nitrogen / 0.79 + 10
  EAD
  8111.26582278481
  </code></pre>
  
  <p>Expected Output:</p>
  
  <pre><code>&gt;&gt;&gt;depth = 90
  &gt;&gt;&gt;mix = 36
  &gt;&gt;&gt;nitrogen = 100 - mix
  &gt;&gt;&gt;EAD = (depth + 10) * nitrogen / 0.79 + 10
  &gt;&gt;&gt;EAD
  67
  </code></pre>
  
  <p>Formats for the numbers:
  self.depth is a natural number (25, 30,35)
  self.mix is a natural number (30, 45, 60)</p>