The following questions are said to be asked during an internship interview for a sales and trading role at London JPMorgan bank
1) I can pay you twice your money every two years, three times your money every three years or four times your money every four years. Which option do you choose and why?
I doubt they would expect you to think about the interest you may earn on your money.
This question obviously depends on how long you plan to work there. (0,2) years and you have what you started with, X.
[2,3) years and the first choice is better, [3,4) second choice better.
I think you can prove that the first choice is always best after 4 years.
[4,6) years is somewhat obvious.
[6,8) years the first choice yields X + 2X + 6X + 18X = 27X
(i.e. start with X, 2X is payment after 2 years, 6X = 2(X + 2X) payment after 4 years, etc.)
Second choice yields X + 3X + 12X = 16X
(same logic as above)
Third choice yields X + 4X = 5X
[8,9) years:
First choice yields X + 2X + 6X + 18X + 54X = 81X
Second choice stays the same, 16X
Third choice yields X + 4X + 20X = 25X
[9,10) years keeps everything but the second choice the same, which changes to 16X + 48X = 64X
I think its pretty obvious from here that shorter reset frequencies are best. Without loss of generality it is assumed that you don't spend any of your money. I'm also assuming "your money" implies total wealth and not your salary.