Answer:
0.5 m/s north
Step-by-step explanation:
Velocity is displacement over time.
v = Δx / Δt
Displacement is the difference between the final position and the initial position. April swims 50 m north, then turns and swims 20 m south. So her displacement is 30 m north.
v = (30 m north) / (60 s)
v = 0.5 m/s north