I assigned a couple of problem to my students today without realizing that these would be too difficult for high school students. However, after starting the problem, I got stumped. I know I am missing something, but what is it? The problem reads as follows: 5. A person walks first at a constant speed of 5.00 m/s along a straight line from point A to point B and then back along the line from B to A at a constant speed of 3.00 m/s. What is a. her average speed over the entire trip and b. her average velocity over the entire trip? Part b is simple, but 'a' is where I got stuck. You know delta x is the same, and you know that t1 and t2 will be different as well. So, delta x = v1*t1, and x=v2*t2. However this leaves us with three unknowns and two equations. What am I missing for my third equation? Thanks!