Answer:
3.3m/s
Explanation:
You first get the total time (80 + 70 = 150s).
Then you would find the displacement of the truck. To do that you would do component method (vector addition), so since its a right triangle (North and East), displacement is 400^2 + 300^2 = d^2.
d= 500m.
So now that you have displacement and time, you can find the velocity:
v=d/t
v=500/150
v=3.3