1. The problem statement, all variables and given/known data Two cars start moving form the same place. One goes north at a rate of 50 mi/hr, while the other heads east at a rate of 30 mi/hr. At what rate is the distance between the two cars changing exactly two hours later? 2. Relevant equations 3. The attempt at a solution I thought that the equation for the velocity vectors is: r(x) = 30xi + 50yj and thus distance d two hours later is given by: d = √(30x² + 50x² ) and dd/dt = ∂x/dt + ∂y/dt and after solving the equation I just plug in 2 for x and y to get what time the distance changes at the two hour mark. Is this right?