Avg. Velocity = Distance Traveled / Time Traveled

[incognito301]

Do you know if these two formulas are the same?

Avg. Velocity = Distance Traveled / Time Traveled

&

Avg. Velocity = V1 + V2 / 2 (V1 = d1/t1 & V2 = d2/t2)

I have a problem that says that a plain goes from a place to another(1) and from there it goes to another place (2).

So:

t1 = 3 h & d1 = 375 km
t2 = 2 h & d2 = 250 km

and using both of the formulas I get the same Average Velocity.
So:

Formula 1 = (375/3 + 250/2)/2 = 125 m/s
.......... ----> Formula 1 = Formula 2
Formula 2 = (375 + 250)/(3+2) = 125 m/s
So I'm guessing they are the same. But my science teacher says they're not.

Do you agree with my teacher? How come?

If you think its right, can you show me a mathematical way to prove it?

Thanks.

P.S. Please answer ASAP.

 

[Doc Al]

You are only getting away with Formula 1 because the velocity is constant in your example. What if it wasn't constant?

Say the plane moved a distance of 300 km in 2 hours, then an additional 300 km in 1 hour. Compare your formulas in this case.