title: Generate random number from 2 different ranges
body: <p>How can I generate a random number from two different ranges?</p>
  
  <p>For example: one number from 10-20 and 50-60.</p>
  
  <p>I know how to generate a random number from one range (1-13):</p>
  
  <pre><code>Random rnd = new Random();
  int num = rnd.Next(1, 13);
  </code></pre>