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**Math Guy****Member**- Registered: 2005-10-12
- Posts: 20

At auction, my brother buys two slightly used Boeing 746's, with the idea of flying one of them around the world. Now, if you buy two of these planes, the auction house throws in a tiny island right on the equator.

Now, everyone knows that the circumference of the earth is 25,000 miles. But, sadly, neither of these planes, which have exactly the same range, can go 25,000 miles on a full tank of fuel.

Tommy does the math, however, and he figures out that if he flies one plane, and I fly the other plane as a refueling plane, I can give him some fuel and I can fly back to the little island

So, at some point, you're going to give me some fuel, you're going to turn back, and I'm going to continue on.

Exactly. We're both going to just make it. I'm going to give you some of my fuel, and with my remaining fuel, I just make it back to the island. And with your initial supply of fuel, plus what I give you from my plane, you continue on your journey, and sometime the next day, if we're lucky, you make it back to the same island.

Having gone all around the world.

Right. So the question is: What's the range of one of these 746's?

There are a few conditions that have to be met. For example, there's no wind, because that would add something complicated to the procedure. And, there's zero time to transfer the fuel and zero time to turn around. And one other thing: The earth isn't rotating for the 24 hours or so it takes to complete this whole thing

*Leave what you think is the right answer

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**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 21,460

Math Guy,

I think the range of the 746 is 18,750 miles. After a flight of 6,250 miles, I give whatever fuel is required in excess of my return of 6,250 miles, i.e. fuel for an additional 6,250 miles. My friend can then comfortably make it!

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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