title: Find percent in mongo
body: <p>I have a collection with 2 docs like below. </p>
  
  <pre><code>{
  _id:1,
  Score: 30,
  Class:A,
  School:X
  }
  {
  Score:40,
  Class:A,
  School:Y
  }
  </code></pre>
  
  <p>I need help in writing query to find out percentage of score like below</p>
  
  <pre><code>{
  School:X,
  Percent:30/70
  }
  {
  School:Y
  Percent:40/70
  }
  </code></pre>