SOLUTION: If Rita receives $40.04 interest for a deposit earning 5% simple interest for 30 days, what is the amount of her deposit? (Round your answer to the nearest cent.)

Use the formula for the simple interest 

    I = P*r*t.


In this formula, I is the interest, which the principal P produces in t years,
if the annual interest rate is r (decimal value).


In your problem,  I = 40.04 dollars (given);  P is unknown (principal);
t = 30 days (= 30/365 of a year) and r = 0.05.


So, you have this equation

    40.04 = .


From this equation, you find

    P =  = 9743.07  (rounded to the nearest cent).    ANSWER

        Notice that the final answer DEPENDS on how you count 30 days.

        You may count them as 1/12 of a year or as 30/365 of a year - the result will be different.

        In order for the resulting number would be unique, the problem MUST INSTRUCT the reader
        on how to count 30 days.