1. The problem statement, all variables and given/known data A rock is thrown from the top of a 20-m high building at an angle of 53 degrees above the horizontal. If the horizontal range of the throw is equal to the height of the building, with what speed was the rock thrown? How long is it in the air? Xf = 20, Xi = 0, Vxi = ?, t = ?, Yf = 0, Yi = 20, Vyi = ?, a = -9.81 2. Relevant equations Xf = Xi + Vxi*t Yf = Yi + Vyi*t + .5(a)(t)^2 3. The attempt at a solution So first, I tried to find the time. I did this by doing 20 = 0 + Xcos(35)*t where X is initial speed and t is time. I then set t = 20/Xcos(35). I then plugged t back into my Yf equation which gives me 0 = 20 + Xsin(35)*(20/Xcos(35)) - 4.905(20/Xcos(35))^2. Solving this for x gives me about 2.7 m/s which is not right. The answer, according to the answer book, is 11 m/s. Can anyone tell me where I'm going wrong?