title: Parent DIV is full width while child div is specific width
body: <p>I'm having a hard time to solve how to accomplish this parent div is full <code>width:100%</code> with specific <code>height:500px</code> then I want the child <code>DIV</code> with specific width and height let's just say <code>width:980px;height = the height of parent DIV</code> then that parent <code>DIV</code> will be divided into <strong>3 columns</strong>. how to accomplish that?</p>
  
  <p>sample image:</p>
  
  <p><img src="https://i.stack.imgur.com/GShoK.png" alt="sample"></p>
  
  <p><strong>GREEN :</strong> Parent DIV with full width.</p>
  
  <p><strong>BLUE:</strong> Child DIV divided into <code>3 columns</code></p>
  
  <p>Thank you in advance! </p>