title: Ruby interpolation in class name
body: <p>I have the following line:</p>
  
  <pre><code>&lt;div class="fact-circle--&lt;%= #{i} %&gt;" data-number="20"&gt;
  </code></pre>
  
  <p>I thought it was possible to interpolate ruby variables like that?</p>
  
  <p>It's choking on the "&lt;" of the opening ERB tag.</p>
  
  <p>Any ideas?</p>