Question

A river flows at 4 km/h. The speed of a boat in downstream is thrice the speed of that boat in upstream. Find out the speed of the boat in still water.

Answer 1

Given,
Speed of the river = 4km/h.
Let the speed of the boat in still water = x km/h.
so speed of the boat in upstream stream = (x-4) km/h.
speed of the boat along the flow of the river (downstream)= (x+4) km/h.
a/q,
x+4= 3(x-4)
=> x + 4 = 3x - 12
=> 2x = 16
=>  x = 8
Therefore speed of the boat in still water = 8 km/h.