Step 1 :Given that Elisa pawned her bicycle for $270 and paid back $285.30 after 17 days, we can calculate the interest she paid as $285.30 - $270 = $15.30.
Step 2 :We know that the simple interest formula is \(I = PRT\), where \(I\) is the interest, \(P\) is the principal amount (the initial amount of money), \(R\) is the annual interest rate, and \(T\) is the time the money is invested for in years.
Step 3 :In this case, we know the principal amount \(P = $270\), the interest \(I = $15.30\), and the time \(T = 17/360\) years.
Step 4 :We can rearrange the formula to solve for \(R\): \(R = I / (PT)\).
Step 5 :Substituting the given values into the formula, we get \(R = 1.2000000000000008\).
Step 6 :Thus, the annual simple interest rate the pawnbroker charged Elisa is \(\boxed{120\%}\).