title: Sum function not working on cells with formulas
body: <p>I have 3 cells with formula. </p>
  
  <p>A1: </p>
  
  <pre><code>=IF(B6&gt;=3.3,"1","0")
  </code></pre>
  
  <p>B1: </p>
  
  <pre><code>=IF(C6&lt;7,"0", IF(C6&lt;9,"1",IF(C6&gt;=9,"2")))
  </code></pre>
  
  <p>C1:</p>
  
  <pre><code>=IF(D6&gt;85,"1","0")
  </code></pre>
  
  <p>my Cell D1 wants to sum up the 3 cells above. </p>
  
  <pre><code>=SUM(A1:C1)
  </code></pre>
  
  <p>but this always returns 0.</p>
  
  <p>but when i do</p>
  
  <pre><code>=A1 + B1 + C1 
  </code></pre>
  
  <p>it returns me my results</p>
  
  <p>why is this so? </p>