Question

On an island, there is an airport that has an unlimited number of identical air-planes. Each air-plane has a fuel capacity to allow it to fly exactly 1/2 way around the world, along a great circle. The planes have the ability to refuel in flight without loss of speed or spillage of fuel. Though the fuel is unlimited, the island is the only source of fuel. You can ignore the time and fuel consumption of refuelling. What is the minimum number of air-planes required to get one air plane all the way around the world assuming that all of the air planes must return safely to the airport?

Answer 1

Answer:

6 planes are required to help one plane all the way around the world.

Explanation:

refuel the main plane fully at these points of its journey.

1. at half of first quarter of journey by one plane.

2. then at end of first quarter of its journey by second plane and third plane assisting second plane to come back to airport.

3 same happening in the last quarter of journey of main plane using 1st and 2nd step.

If main plane is refuelled at these locations then all other planes can come back safely and main plane completes a circle around the world.