Find Average Speed

zig

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Jan 19, 2012
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Here's the Problem. A motorist traveled from Town P to Town Q. After Traveling 1/3 of the trip at an average speed of 45 km/h, he continued to travel another 240 km to reach town Q
(a) Find the distance between the two towns. I found that to be 360 km
(b) If his average speed for the whole trip was 54 km/h, find his average speed for the last 2/3 of the trip.

I set it up this way: (45km/h+?km/h) / 2 = 54 km/h I got the answer of 63 km/h. The answer book says it is only 60 km/h? What am I doing wrong?
 
Find Average Speed Thanks

Thanks for the help. Wow! I was way off. I did know that formula so I should have figured it out. Thanks for showing me how.

zig
 
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