title: Excel: why is the average of divisions different from division of sums?
body: <p>So lets say I have two variables <code>x</code> and <code>y</code>. I calculate the total sum of each variable. </p>
  
  <p>I calculate <code>y/x</code> for each row and also calculate <code>y/x</code> for the sum of both <code>x</code> and <code>y</code> columns (280/10=28).  </p>
  
  <p>I would expect this value (28) to be equal to the average of <code>y/x</code> (230/4=32.5), but it is different. </p>
  
  <p>This might have a simple explanation, but I can't seem to find it. </p>
  
  <p><img src="https://i.stack.imgur.com/Wpci0.png" alt="An example here"></p>
  
  <p>Thanks in advance </p>