title: mongodb multiply aggregation operator
body: <p>Say I have the following aggregation :</p>
  
  <pre><code> db.a.aggregate(
     [
       { $project: {  total: { $multiply: [ 4533, 0.0001 ] } } }
     ]
  )
  </code></pre>
  
  <p>The output of this aggregation is <strong>0.45330000000000004</strong> when it clearly should be <strong>0.4533</strong>. Is this a bug in the aggregation framework? </p>