a car moves from car A to B covering a distance of 600km/h if it covers first 400km at 80km/h and the other remaining at 100km/h .What is the average speed for entire journey
time at 80
t1 = 400/80
time at 100
t2 = 200/100
total time = t1 + t2
av speed = 600 / (t1+t2)