title: Rails 3. How to display two decimal places in edit form?
body: <p>I have this edit form.</p>
  
  <p>But when I store something such as 1.5, I would like to display it as 1.50. </p>
  
  <p>How could I do that with the form helper? <code>&lt;%= f.text_field :cost, :class =&gt; 'cost' %&gt;</code></p>