How Do You Calculate Average Speed with Variable Acceleration?

[YMMMA]

Homework Statement

In the file below.

Homework Equations

Speed= total distance over total time.
Acceleration = change of speed over time

The Attempt at a Solution

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I tought it is just E because of the first rule above. But then I doubt my answer since it moved with constant acceleration first then constant speed. However, I don’t see thant any of the choices fit. Can someone help?

 

[PhanthomJay]

Your definition for speed is actually the definition for average speed. What is the total distance and what is the total time?

 

[YMMMA]

Sum of distance and sum of time?

 

[PhanthomJay]

What is the sum of the distances? How much time elapsed in covering those distances?
Hint: for total time, try replacing t1 and t2 with numerical values to get an idea of total time in letter variables.

 

[YMMMA]

Is it not d1+d2 for total distance? Aha, the hint makes this clear; it is just t2.
Next time I will assume some values. Thanks a lot.

 

[PhanthomJay]

Well, I made the same mistake at first.