Combining list in a Cartesian product format with addition operation?

Question

I have two list to begin with.

list1 = {1, 2, 3};
list2 = {10, 20, 30, 40};

I want to obtain the following output (order unimportant):

{11, 12, 13, 21, 22, 23, 31, 32, 33, 41, 42, 43}

I can obtain it via "Table, For, Do" etc. command but I am looking for a concise code to achieve such an output?

Answer 1

Outer[Plus, list2, list1] // Flatten

Answer 2

A variation of Coolwater's answer:

Tuples @ Unevaluated[{10, 20, 30, 40} + {1,2,3}]

{11, 12, 13, 21, 22, 23, 31, 32, 33, 41, 42, 43}

Answer 3

list1+#&/@list2//Flatten

(*{11,12,13,21,22,23,31,32,33,41,42,43}*)

Answer 4

Total[Tuples[{list2, list1}], {2}]
(* {11, 12, 13, 21, 22, 23, 31, 32, 33, 41, 42, 43} *)