Downstream speed =9 + 6=15 km/hr Upstream speed=9-6 = 3 km/hr Let the distance from A to B is x km. downstream distance=x, upstream distance is half ofx because boat goes half way upstream, then x/15+(x/2)/3 = 70 Sox=300 Therefore, distance covered by boat = 300 + 300/2 = 300+150 = 450 km