Solution:Speed of upstream = (42 × 60)/63 = 40 km/hr
Speed of current : Speed of still water = 3 : 7
Speed of upstream = Speed of boat in still water - speed of Current
40 = 4x
=> x = 10
Speed of current = 30 km/hr
Speed of boat in still water = 70 km/hr
Speed of downstream = Speed of boat in still water + speed of Current
=> 70 + 30 = 100 km/hr
Speed = 100 km/hr, Time = 42 minutes
Distance = 100 × (42/60) = 70 km