I have the following table called products:

|id| |name|
 81   monitor
 82   keyboard
 83   mouse
 84   headphone

The controller is products_controller.rb with the following code:

 def index
   @products = Product.all
 end

It should display the following result

|Nº|  |name|         |Nº|   |name|
 1     monitor        3      mouse 
 2     keyboard       4      headphone

I tried the following code using SLICE:

<table>
  <tr>
    <td>Nº</td>
    <td>Product</td>
  </tr>
  
  <% @products.each_slice(2).each_with_index do |grouped_array,row_index| %> 
  <tr>
     <% grouped_array.each_with_index do |array, column_index| %>
     <td><%= column_index + 1 %></td>
     <td><%= array.name %></td>
     <% end %>
  </tr>
  <% end %>
</table>

The result using SLICE was:

|Nº|  |name|         |Nº|   |name|
 1     monitor        1      mouse 
 2     keyboard       1      headphone

I tried using in_groups_of

  <% @products.in_groups_of(2).each_with_index do |grouped_array,row_index| %> 
  <tr>
     <% grouped_array.each_with_index do |array, column_index| %>
     <td><%= column_index + 1 %></td>
     <td><%= array.name %></td>
     <% end %>
  </tr>
  <% end %>

The result using in_groups_of was:

|Nº|  |name|         |Nº|   |name|
 1     monitor        1      mouse 
 2     keyboard       1      headphone