Hello,

if I understand your problem correctly you have

x = 0.122222222.... then

10x = 1.22222222.... thus

9x = 1.1 Therefore

If you invest a capital of at an interest o p % then the capital grows in n years to

Now plug in the values you know:

. Divide by 10000 and calculate the 4th root:

. Solve for p.

I got