Vectors quantity have magnitude and direction, which means
that they can be solved arithmetically with their corresponding signs. In this
case, we can simply add the two velocities to get for the final velocity of the
plane. But first let us determine the signs of each velocity value.
As a reference, we take the direction of the plane to be
going the positive y-axis. Therefore it is going up and positive. Now take note
that the wind is a “tailwind” which means that the wind is going WITH the
direction of the plane, therefore it is also a positive. Now knowing that, we
can add the two:
Final velocity = 300 km / hr + 20 km / hr
Final velocity = 320 km / hr