text_field_tag doesn't display after upgrade Rails from 2.3.18 to 4.0.4


I developed a few simple apps using Ruby On Rails (no database) for researchers, we
got a new server (Mac Pro) and I try to develop in rails 4.0.4, I have this piece of
code in index.rhtml, but not anymore if I copy it to index.html.erb, I don’t get
any error, but text_field_tag and submit_tag are not displaying, I read manuals
about form_tag, text_field_tag and submit_tag, they don’t seem to change
much, what I might be doing wrong? Thanks a lot for your advice.

Sample size calculation

<% form_tag('/progress') do %>
      <td> Condition Number : </td><td><%= text_field_tag( "cond", value = nil, :size => "10" )    %></td>

      <td> Number of People : </td><td><%= text_field_tag( "no", value = nil, :size => "10" )    %></td>

      <td> <div><%= submit_tag "Compute" %></div></p>
<% end %>

In rails 3 and above you need to use <%= for form_tag


Thanks a lot!