This riddle must be done IN YOUR HEAD and NOT using paper and a pen

[1smartengineer]

Take 1000 and add 40 to it. Now add another 1000.
Now add 30. And another 1000.
Now add 20. Now add another 1000. Now add 10.
What is the total?

Now check it with a calculator, the brain sure knows how to play little tricks on us, doesn't it?

[Heinz R.]

4100. If any engineer gets this wrong, even doing it in one's head, have him/her turn in his/her degree.