Noelle walks from point A to point B at an average speed of 3 kilometers per hour. At what speed, in kilometers per hour, must Noelle walk from point B to point A so that her average speed for the entire trip is 5 kilometers per hour?  Choose the correct answer:
A) 15
B) 12.5
C) 10
D) 8
E) 7.75
Let's suppose that speed while returning was xkm/h   Since the distance is same, we can apply the formula of avg speed   15vg speed= 2S1S2/S1+S2   5= 2*3*x/3+x   x= 15   15 is the answer
<result>A</result>
Noelle walks from point A to point B at an average speed of 3 kilometers per hour. At what speed, in kilometers per hour, must Noelle walk from point B to point A so that her average speed for the entire trip is 5 kilometers per hour?