posted by nikita .
An airplane travels 2800 km at a speed of 700 km/h, decreases its speed to 500 km/h for the next 1500 km and travels the last 1000 km at a speed of 400 km/hr. Find the average speed of the plane for the trip.
How you get yhe answer
Add the total distances up: 2800+1500+1000=5300 km
Solve for time for all parts (remember units)
Part A: 2800/700=4 hours
Part B: 1500/500=3 hours
Part C: 1000/400=2.5 hours
Then add all time parts up
Then finally solve for speed total
speed=5300 km/9.5 hours