Velocity of the boat, v b = 51 km/h
Velocity of the wind, v w = 72 km/h
The flag is fluttering in the north-east direction. It shows that the wind is blowing toward the north-east direction. When the ship begins sailing toward the north, the flag will move along the direction of the relative velocity ( v wb ) of the wind with respect to the boat.
T he angle between v w and (– v b ) = 90° + 45°
Angle with respect to the east direction = 45.11° – 45° = 0.11°
Hence, the flag will flutter almost due east.