Rely Solely On Your Mental Processes To Accomplish This Task, Avoiding The Use Of Calculators Or Written Notes

The Question

The Answer Is:
Begin with 1000. Next, add 40, followed by another 1000. Then, add 30, followed by yet another 1000. Add 20, then include one more 1000, and finish by adding 10.

The sum is calculated as follows:

1000 + 40 + 1000 + 30 + 1000 + 20 + 1000 + 10 = 4090.