To solve for t, you will use the equation given: -16t^2 + 16t + 480 = 0. First, simplify the equation by dividing everything by 16: -t^2 + t + 30 = 0. Then complete reverse FOIL: (-t + 6)(t + 5) = 0. Next, set each of these equations to 0 separately, and solve for t. You will get t = 6, and t = -5. Since time can't be negative (Rose can't have hit the water after a negative number of seconds), the answer is 6.