The resultant velocity of the plane is the sum of the two velocity vectors which are perpendicular to each other. See the attached figure.
The magnitude of the resultant velocity is
.
The approximate value of the actual velocity of the plane is . Correct choice is (D).
check the picture below.
so, when we have a line from a 90° angle running perpendicular to the opposite side, like in this case, we end up with three similar triangles, a large one containing the other two, a medium and a small one.
now, using the sides proportions as you see there, of the small and large one, we get that much.
