A drone's path relative to the ground follows the four equal sides of a square, travelling east, north, west and south in that order. The wind velocity is constant throughout the flight, and the drone keeps the same speed relative to the air on every side.
Its speeds relative to the ground on the east, north and south sides are , and metres per second, respectively.
The drone's velocity relative to the ground is the vector sum of its velocity relative to the air and the wind velocity.
Ignoring time spent turning at the corners, what is the drone's average speed relative to the ground for the whole circuit, in metres per second?
A
B
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D
E
F