hi guys im playing with RoR with the environment of rails 3 ruby 1.9 i got stuck in nil can't be coerced into BigDecimal error i need to get the total cost of the products inside the cart i know where the problem is(i think) but i almost did every thing cart/show.html.rb <div class="cart_title" >Your Cart</div> <table> <% for item in @cart.line_items %> <tr> <td><%= item.quantity %>×</td> <td><%= item.product.title %></td> <td class="item_price" ><%= number_to_currency(item.total_price) %></td> </tr> <% end %> <tr class="total_line" > <td colspan="2" >Total</td> <td class="total_cell" ><%= number_to_currency(@cart.total_price) %></td> </tr> </table> <%= button_to 'Empty cart', @cart, :method => :delete, :confirm => 'Are you sure?' %> model/line_item.rb def total_price line_items.to_a.sum { |item| item.total_price } end model/cart.rb def total_price product.price * quantity end my second option is def total_price if product.price product.price * quantity else product.price = "0.0".to_d end end but still this wont work thanks more power to us!