title: F# Using Return Values From Async
body: <p>I'm trying to learn F# but I keep running into issues. The latest is using async. In the code below, I'm trying to run two long running operations and perform a calculation based on the result but I get an error "Async does not support the + operator". I have tried casting etc to get it to work but I'm not getting anywhere fast.</p>
  
  <p>Could someone please explain where I'm going wrong.</p>
  
  <p>Thanks.</p>
  
  <pre><code>let SumOfOpFaults =
      async{
          printfn "Getting Sum of Op Faults"
          return query {
              for a in AlarmResult do
              sumBy a.UserFaultTime
          }
      }
  
  let SumOfMcFaults =
      async{
          printfn "Getting Sum of Machine Faults"
          return query {
              for a in AlarmResult do
              sumBy a.MachineFaultTime
          }
      }
  
  [SumOfMcFaults; SumOfOpFaults]
  |&gt; Async.Parallel
  |&gt; Async.RunSynchronously
  |&gt; ignore
  
  let total = SumOfOpFaults + SumOfMcFaults // &lt;---Error Here
  </code></pre>