If you consider a simple interest, use the following formula:
I = p x r x t
where p is the initial investment ($11,300), r is the interest rate (3.75%) and t the ime in years. I is the final amount of money ($3,813.75).
Solve the previous equation for t and replace the values of p, I and r:
t = I/(p x r)
t = (3,813.75)/(11,300 x 0.0375)
t = 9
Hence, 9 years allow you to earn $3,813.75
