gistfile1.js

   $(function () {

        $("select#Rooms").val("0");
        $("select#room_Children").val("0");
        $("select#room_Children_ChildrenAges").val("0");

        var rooms = 4;

        for (var room = 1; room <= rooms; room++) {
            $("div.room#" + room).hide();
            $("div.room#" + room).find('select#room_Children_ChildrenAges').closest('div.control-group').hide();
        }

        $("select#Rooms").change(function () {
            for (room = 1; room <= rooms; room++) {
                if ($(this).val() >= room) $("div.room#" + room).slideDown('slow');
                if ($(this).val() < room) $("div.room#" + room).slideUp('slow');
            }
        });

        $('select#room_Children').change(function () {

            var children = 3;
            
            for (var child = 0; child <= children; child++) {
                
                if ($(this).val() > child) {
                    
                    $(this).closest('div.room')
                        .find('select#room_Children_ChildrenAges')
                        .eq(child).parent('div.controls').parent('div.control-group').show();
                }

                if ($(this).val() <= child) {
                    
                    $(this).closest('div.room')
                        .find('select#room_Children_ChildrenAges')
                        .eq(child).parent('div.controls').parent('div.control-group').hide();
                }   
            }          
        });
    });