Noelle walks from point A to point B at an average speed of 4 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 6 kilometers per hour? Select:  A) 6.75  B) 7  C) 8  D) 12  E) 14
Let's suppose that speed while returning was xkm/h   Since the distance is same, we can apply the formula of avg speed   Avg speed= 2S1S2/S1+S2   6= 2*4*x/4+x   x= 12   12 is the answer
<result>D</result>
Noelle walks from point A to point B at an average speed of 4 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 6 kilometers per hour?