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Old Oct 1st 2016, 07:05 AM   #1
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Simple average speed problem

This should be very easy, I have a feeling I'm missing soemthing obvious as the web form won't accept any of my answers.

"A jet takes off from SFO (San Francisco, CA) and flies to ORD (Chicago, IL). The distance between the airports is 3000 km. After a 1-h layover, the jet returns to San Francisco. The total time for the round-trip (including the layover) is 9 h, 34 min. The westbound trip (from ORD to SFO) takes 26 more minutes than the eastbound portion.

What is the average speed for the overall trip? (Express your answer to three significant figures.)"

so 9 hours 34 mins = 9.57 hours. 3000km/9.57h= 313.48 km/h. But the web form won't accept this answer nor rounding to 313, 313.5, or 314.
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Old Oct 1st 2016, 08:53 AM   #2
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Sounds like you're on top of things, and have correctly discerned between average speed and average velocity (the latter being zero in this case since the start and end points are the same yielding total displacement of zero).

But, alas, you've got a boo-boo in there. The distance between the airports is 3000km, and the plane is taking a round trip. So what's the total distance traveled? Not 3000km.
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Old Oct 1st 2016, 08:58 AM   #3
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Originally Posted by CorneliusXI View Post
Sounds like you're on top of things, and have correctly discerned between average speed and average velocity (the latter being zero in this case since the start and end points are the same yielding total displacement of zero).

But, alas, you've got a boo-boo in there. The distance between the airports is 3000km, and the plane is taking a round trip. So what's the total distance traveled? Not 3000km.
Thank you! I knew it had to be something obvious like that that I was missing. Appreciate the hint.
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