title: Spreadsheets: how do I SUM values in a column, only if the text column has a 1?
body: <p>Let's say I have this data</p>
  
  <pre><code>4     1
  4     0
  4     1
  3     0
  5     1
  </code></pre>
  
  <p>How do I write a function (using <code>SUM</code> or something like that) to add all the values on the left, if the values on the right are 1, or true</p>
  
  <p>The total should be 13</p>