Question

A river current has a velocity of 5 km/h relative to the shore. A boat moves in the same direction as the current at 4 km/h relative to the river.

How do you calculate the velocity of the boat relative to the shore?


divide the river’s velocity by the boat’s velocity

subtract the boat’s velocity from the river’s velocity

add the river’s velocity to the boat’s velocity

Answer 1

To calculate the velocity of the boat relative to the shore, you need to add the boat's velocity relative to the river to the river's velocity relative to the shore.

In this case, the river has a velocity of 5 km/h relative to the shore, and the boat is moving at 4 km/h relative to the river in the same direction. The calculation would be:

\[
\text{Velocity of the boat relative to the shore} = \text{Velocity of the river} + \text{Velocity of the boat relative to the river}
\]
\[
= 5 \text{ km/h} + 4 \text{ km/h} = 9 \text{ km/h}
\]

Therefore, the correct method is to **add the river’s velocity to the boat’s velocity**.