title: Sum of floats: unexpected result
body: <p>The following output surprised me:</p>
  
  <pre><code>1.1 + 2.2
  =&gt; 3.3000000000000003
  </code></pre>
  
  <p>An unexpected small digit came up from the sum. The same does not happen for other addends, e.g.:</p>
  
  <pre><code>3.0 + 0.3
  =&gt; 3.3
  </code></pre>
  
  <p>I tried both in Python 2.7 and in 3.4, but the result is the same. What is the reason for this unexpected result of the sum?</p>