Final answer:
The boat's actual velocity is 4 knots. (Option B is the correct answer).
Step-by-step explanation:
To determine the boat's actual velocity, we need to calculate the resultant velocity. We can do this by using vector addition. The boat's velocity can be represented as a vector with a magnitude of 6.1 knots and a direction of 135°. The current's velocity can be represented as a vector with a magnitude of 1.1 knots and a direction of 330°. Adding these vectors together will give us the resultant velocity.
To add the vectors, we can break them down into their x and y components using trigonometry. The x-component of the boat's velocity is 6.1 * cos(135°) = -4.31 knots. The y-component of the boat's velocity is 6.1 * sin(135°) = 4.31 knots. Similarly, the x-component of the current's velocity is 1.1 * cos(330°) = 0.95 knots, and the y-component is 1.1 * sin(330°) = -0.60 knots.
Adding the x-components and the y-components separately, we get a resultant velocity of (-4.31 + 0.95) knots in the x-direction, and (4.31 - 0.60) knots in the y-direction. Using the Pythagorean theorem, we can calculate the magnitude of the resultant velocity as sqrt((-4.31 + 0.95)^2 + (4.31 - 0.60)^2) = 4 knots.