1) Dan is crossing a river from point A to point B. The distance between the points are 60 meters, and B are straight on the other side of the river from A. The river current is 0.5 meters / second towards the right and Dan's rowing speed is 2 m/s. Find the point C Dan has to aim for to end up at point B. I've found the following: - He will use 30s ( 60m / 2ms ) rowing across the river. - If he crosses the river directly towards B he will end up 15m (30s * 0.5ms) to the right of B. - The speed of the boat when rowing directly towards B is ~= 2,06ms ((2^2 + .5^2)^.5) But I cant seem to formulate a good recipe for finding the point C. 2) Select two points A and B on the X-axis. Find the point P which divides the line segment AB into 1:2, that is so AP : PB = 1 : 2. Using vectors, show that the X coordinate of the point P can be described by (2A + B) / 3. I can see that the relationship can be described as "OP = OA + 1/3 AB" or "OP = OB - 2/3AB" but nothing that i can manipulate until i get it into the form (2A + B) / 3.