Question

A sailor climbs a mast at 0.5 m/s on a ship travelling north at 12 m/s, while the current flows east at 3 m/s. What is the speed of the sailor relative to the ocean floor?

Answer 1

assuming the usual orientations, the resultant is
v = 3i + 12j + 0.5k
so the speed is |v| = √(3^2 + 12^2 + 0.5^2) = 12.38 m/s

Answer 2

horizontal speed = sqrt (3*2 + 12*2)
vertical speed= 0.5
so speed = sqrt ( 3^2+ 12^2 + 0.5^2)
luckily the question did not ask for velocity :)