The speed of a boat in still water is 25 km / hour. The time taken by this boat to go downstream of distance 120 is 4 hours. Find the speed of the stream/water.

It is 5 km/hour

Step-by-step explanation:

Let w represents the speed of the water

The speed can be found by following:

→ distance = speed x time → speed = distance / time (1)

If the boat goes downstream the total speed of the boat is the speed of the boat in still water + the speed of the water. Substitute the values into equation 1:

→ (the speed of the boat in still water + the speed of the water) = 120 / 4

Since the speed of the boat in still water is 25

→ 25 + w = 120 / 4

→ w + 25 = 30

→ w = 5