Question

How much would an initial investment of $500 be worth in 90 days if it earned 3% daily?

Answer 1

I am sure you meant
3% per annum, compounded daily

i = .03/365 = .000082191

amount = 500(1.000082191)^90 = 503.71


If you actually meant 3% per day, wow, ...

amount = 500(1.03)^90 = 7150.23

Answer 2

sharon is that you?