Question

a car covers 30 km/h at a uniform speed of 30km/h.What should be its speed for the next 90 km/h if the average speed for the entire journey is 60 km/h

Answer 1

Total distance = 30+90=120
if avg. spd is 60 km/h then total time to cover the dist. is 2 hour.
avg spd.= (30+x)/2

distance=spd * time

120=(30+x)/2*2
120=30+x
x=120-30=90
i.e spd = 90 km/h