Okay, so I thought I was on the right track with this problem, but clearly I haven't been getting the right answer!(adsbygoogle = window.adsbygoogle || []).push({});

The problem is as follows :

A physics instructor drives down to St. Louis to see his mom. Coming back, he drives the first half thedistanceat 65 km/hr and the second half of thedistanceat 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...

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

So...t initial = x initial / 65km/hrandt final = x final / 100km/hr

Then I plugged those into the equation foraverage velocity = change in x / change in t

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

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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! :)

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# Homework Help: Help With Problem About 1-D Motion

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