A watercraft is rowed down 32 km along a river in 4 hours and 10 km against the river in 5 hours. Find the speed of the watercraft and that of the river.
Answer & explanation
Correct answer: option 3
We know that,
Upstream Speed = Speed of Boat – Speed of current
Downstream Speed = Speed of Boat + Speed of current
Distance = Speed × time
Let the speed of watercraft be x and river be y
Time taken by watercraft while moving down for 32 km is 4 hours
In one hour = 8 km/h = x + y ----(1)
Time taken by watercraft while moving against for 10 km is 5 hours,
In one hour = 2 km/h = x + y ----(2)
On solving the equation (1) and (2)
x = 5 km/h and y = 3 km/h