Question

Ann has walked 8 km with a velocity of 4 km/h. Now she will run some time with a velocity of 8 km/h.How long does she have to run in order to have an overall average velocity of 5 km/h?
SOMEONE PL Z ANSWER IT AND TELL ME THE METHOD

Answer 1

distance1 = 8km
velocity1 = 4km/h
time taken = distance/ velocity , = 8/4 = 2h


again,
velocity2 = 8km/h
let the time be "t"
then, the distance becomes velocity × time = 8t km.


average velocity = total distance / total time taken

5km/h = (8 + 8t) / ( t+ 2)
5(t+2) = 8+8t
5t+10 = 8+8t
2 = 3t
t =2/3h


Therefore, she has to run at approximately 0.66 hr to get the desired average velocity.