title: Sass: Multiply sum of px to rem function
body: <p>I'm trying to multiply the sum of a calculation performed in a function but I get the following error:</p>
  
  <p><code>"Undefined operation: "pxToRem(4) times 3"</code></p>
  
  <p>Whilst I could use rems directly it's a lot easier for me to work in pixels. Can anyone tell me why I'm getting this error and if there's a way to solve it? I'm not trying to multiply a string and I'm not multiplying a unit by a unit so I don't understand where the problem is.</p>
  
  <pre><code>// Declare px to rem function
  $browser-context: 16;
  @function pxToRem($pixels, $context: $browser-context) {
    @return ($pixels / $context) * 1rem;
  }
  
  // Call the px to rem function
  $column-unit: pxToRem(4);
  
  // Multiply sum of px to rem function
  $column-span: $column-unit * 3;
  </code></pre>
  
  <p>Thanks for any help.</p>