A small boat moving at 15 km/h crosses a 350 m wide river. The water runs at 6 m/s towards the left. Calculate: (4) 5.1 The resultant velocity of the boat.

To calculate the resultant velocity of the boat, we need to take into account the velocity of the boat and the velocity of the water current.

Let's first convert the boat's speed from km/h to m/s:
15 km/h * (1000 m / 1 km) * (1 h / 3600 s) = 4.17 m/s

The boat is moving to the right at 4.17 m/s relative to the water.

Next, we need to find the velocity of the water current relative to the ground. Since it's moving towards the left at 6 m/s, we can add these velocities together:

4.17 m/s (boat) - 6 m/s (current) = -1.83 m/s

The resultant velocity of the boat is -1.83 m/s, indicating that the boat's motion relative to the ground is towards the left at a speed of 1.83 m/s.