- #1

- 33

- 0

The problem is as follows :

A physics instructor drives down to St. Louis to see his mom. Coming back, he drives the first half the

*distance*at 65 km/hr and the second half of the

*distance*at 100 km/hr.

**What is his average speed coming back from St. Louis ?**

Okay, so I was trying to determine the t for the two distances and did the following work :

Well I was going to just post a scan of my work, but it says I can't so I'll just give some of what I did...

---

I used t=x/v to solve for the initial t and final t.

So...

*t initial = x initial / 65km/hr*and

*t final = x final / 100km/hr*

Then I plugged those into the equation for

*average velocity = change in x / change in t*

So...

*V avg = (x - x initial) / [(x / 100) - (x initial / 60)]*

---

I think I've gotten to the right point, but if the initial distance and final distance are the same I would just get zero, so I know I'm doing something wrong. Any help would be appriciated! :)