# For at least one plane to finish a trip around the world, how many planes do you need at least?

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There is an air base on the equator. The maximum amount of fuel that a plane can contain would be only sufficient for it to fly halfway around the world.

For at least one plane to finish a trip around the world, how many planes do you need at least?

A trip around the world!
Logic Level 3

There is an air base on the equator. The maximum amount of fuel that a plane can contain would be only sufficient for it to fly halfway around the world.

For at least one plane to finish a trip around the world, how many planes do you need at least?

Details and assumptions:
Same plane doesn't depart twice or more.
The airplanes can use their fuel until it's empty. Starting the airplane doesn't take any time.
Every plane moves at the same speed, and on the same airway.
Assume the planes and air base are dimensionless, and thus, can turn directions instantly.
The plane can only be fueled via aerial refueling, and the amount of time the process takes is negligible.
Every plane starts at the air base and must return to the air base.

posted Jul 21, 2017

if the same plane can get refueled, one is sufficient to go round the world over the equator, OTHERWISE
three because there is remote likelihood of starting the second plane where the first has run out of fuel

Mine is coming as 5, can you explain you logic with three planes.

Similar Puzzles

There are a group of airplanes on an island. The tank of each airplane contains just enough fuel to fly halfway around the world. Any amount of fuel can be transferred from one plane to another while in the air. The only fuel source is on the island. It is assumed that all planes burn fuel at the same rate and fly at the same speed.
What is the smallest number of airplanes needed to ensure the complete flight of one plane around the world?
All planes should return safely to the island.

+1 vote

Maram was planning to take a trip around the world. She enjoyed visiting locations that resembled her name. So she drew up her travel plans and came up with the following places she would be visiting.

However in her haste she erred on one location. Can you tell us which one?

Herewith is the list:

Ekalaka Lake - Montana, USA
Mullum Mullum - Victoria, Australia
Klein Karoo - South Africa
Zirak Kariz - Afghanistan