A van drive 17.5km north. Then it turns west and drives 9.1km. The van then drives 14.5km south. The entire trip takes 40 minutes. What is the average velocity of the truck?

Question

I know avg velocity is displacement/time elasped, but I can not figure out what the displacement it....i gt 12.1km but when i dived by time the answer is wrong.....can you show steps on how to solve this?

Thanks!