Julie drives 100 mi to Grandmother's house. On the way to Grandmother's, Julie drives half the distance at 33.0 and half the distance at 80.0 . On her return trip, she drives half the time at 33.0 and half the time at 80.0 .
What is Julie's average speed on the way to Grandmother's house?

Question

Julie drives 100 mi to Grandmother's house. On the way to Grandmother's, Julie drives half the distance at 33.0  and half the distance at 80.0 . On her return trip, she drives half the time at 33.0  and half the time at 80.0 .
What is Julie's average speed on the way to Grandmother's house?

turingtest · Answer

reprint
already answered

turingtest · Answer

...unless someone wants to plug in the numbers for you that is http://openstudy.com/study#/updates/4f1e3b56e4b04992dd24a260

anonymous · Answer

(33.0+80.0)/2=56.5

from this formula ==>  average speed = (V1+V2+V3+...)/n

jamesj · Answer

Very importantly, what alismart has written is false in general.  

For example, if I drive 
- 30 km in one hour                (v1 = 30 km/hr)
followed by
- 30 km in the next 1/2 hour  (v2 = 60 km/hr)

then my average speed from first principles is

Average speed = (distance)/(time)
                       = (60 km)/(1.5 hours) 
                       = 40 km/hr

Using  alismart's formula, the average speed would be
$$ \frac{30 + 60}{2} = 45 $$
which is wrong.

anonymous · Answer

then if you want to bring distance the complete formula will be :
x=distance        ==>

anonymous · Answer

|dw:1327423607110:dw|