jQuery count child elements

<div id="selected">
  <ul>
    <li>29</li>
    <li>16</li>
    <li>5</li>
    <li>8</li>
    <li>10</li>
    <li>7</li>
  </ul>
</div>

I want to count the total number of <li> elements in <div id="selected"></div>. How is that possible using jQuery’s .children([selector])?