After driving 20.0 km west, a car turns southwest and proceeds another 80.0 km. What is the displacement (in kilometers) of the car from the point of origin (magnitude only)?
The displacement is the sum of the two vectors.
Add the west and the south components of the two legs of the journey:
South: 80 sin 45 = X
West: 20 + 80 cos 45 = Y
magnitude of displacement = sqrt(X^2 + Y^2)