physics
posted by mattie .
A person walks first at a constant speed of 4.90 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 2.70 m/s.
(a) What is her average speed over the entire trip?

She is travelling the same distance at each speed, so it doesn't matter what that distance is. You simply find the average of the two speeds.

The answer is NOT the average of 2.7 and 4.9. I answered this question earlier. Why are you posting it again?
http://www.jiskha.com/display.cgi?id=1283304487 
Vectors and have equal magnitudes of 49.0. If the sum of and is the vector 16.3 , determine the angle between and .