I'm having trouble differentiating between the definition of average in physics and a traditional average. For example, say a car travels 100km for 2 hours then travels 80km for 1 hour. The average speed for the first portion is 50km/hr and the average speed for the second portion is 80km/hr. Here is where I have an issue. The average speed for the entire trip is 60km/hr(total distance over total time), but taking a traditional direct average where you add everything and divide by the sum of how many things you added together, I get 65km/hr. Why are these different? If anyone can define these two types of averages for me, I'd greatly appreciate it.