Please answer the following question by reasoning step-by-step.
At what rate percent on simple interest will a sum of money double itself in 30 years?\nOptions:\n(A) 3 1/3%\n(B) 3 1/9%\n(C) 3 9/3%\n(D) 3 2/3%\n(E) 3 6/3%

(A)
P = (P*30*R)/100\nR = 3 1/3%.

The answer: (A)