If a car travels 60 mi. north for one-half hour, 100 mi. west for one hour, and 60 mi. south for 30 minutes, what is the total displacement of the car?
The first and the last segment ... 60 mi north and 60 mi south ... canceled each other. The only segment left is the 100 mi west, so that's the overall displacement ... 100 miles west. The times don't matter at all.