### Brain Teasers

# Planes Apart

Two planes fly once around the world together.

They both fly at a constant distance above the

surface of the Earth, one above the other.

On completion, one of the planes has travelled

two kilometres further than the other.

(Assume the Earth is a perfect sphere.)

How far apart (in metres) were the two planes?

They both fly at a constant distance above the

surface of the Earth, one above the other.

On completion, one of the planes has travelled

two kilometres further than the other.

(Assume the Earth is a perfect sphere.)

How far apart (in metres) were the two planes?

### Answer

1000/pi [or 318.3 metres]Hide Answer Show Answer

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## Comments

mad ade I firmly believe you like math, and that is a good thing.

If there's one bad airplane teaser, I haven't heard it!!

An explanation would have been good though - for the benefit of the non mathematical geniuses amongst us

The formula for circumference of a circle is C = 2*Pi*r. Apply a little bit of calculus and Î´C = 2*Pi*Î´r. 2000 = 2*Pi*Î´r. So the change in radius Î´r = 2000/2Pi = 318.3 m

A nice variation on an old teaser.

A nice variation on an old teaser.

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