Answer:
The answer is below
Step-by-step explanation:
The speed of the boat in still water is perpendicular to the speed of the water flow. Therefore the speed relative to the ground (V), the speed of flow and the speed of the boat in still water form a right angled triangle. Hence the speed relative to the ground is given as:
V² = 56² + 126²
V² = 19012
V = 137.9 m/s