a truck travels at 90km/hr W for 10 min. then at 110 km/ hr for 38 km what was the trucks average velocity
I am assuming that the truck is traveling West the whole time.
I would start by calling the 90 km/hr section part 1 and the 110 km/hr section part 2. Then convert the 10 min into hours to make your life easier. It comes out to be 0.17 hours. (10/60=0.16666...) Next figure out the time for part two using the definition of velocity, v= d/t where v is velocity, d is displacemnet and t is time. Turns out it traveled for 0.35 hr.
Now there's probablly an easier way to do this, but this is how I know.
First figure out how far the truck went in part one by multiplying the velocity by the time. Should come out to be 15.3 km. Then do the same for part two. It should be 38.5 km.
Then use the equation Vavg=(d)/(t) where Vavg is the average velocity, d is the total distance traveled and t is the total time. Divide them and you'll have your answer.
I would NOT use the decimals I rounded to and solve it again, but this should give you an idea of how to work the problem. Hope it helps.