M25

[bednobs]

If 2 cars started at the same point and one went anticlockwise and one went clockwise, and finished in the same place they started, how much difference in mileage would there be (if any) between them?
(so would the anti clockwise one cover less miles?

[Buenchico]

To be pedantic, you couldn't do either journey without leaving one end of the M25 and then rejoining it at the other end. The Dartford Crossing isn't part of the M25. (It's the A282).

This isn't the first time that the question has been asked. See here:
http://www.theanswerb...g/Question166831.html
or, for some real fun reading, try here!
http://www.pistonhead...20vs%20anticlockwise.

Chris

[bednobs]

thanks Chris!
I am actually none the wiser :)

[DTCwordfan]

Obviously bedknobs is lost in Surrey - most people are.

[New Judge]

The difference in circumference between two concentric circles is 2pi times the difference between the radius of the two circles.

So, working on the assumption that the M25 is circular (although it is not, the opposite curves will cancel each other out) and assuming the distance between lane one of the anti-clockwise carriageway is about 80 feet nearer the centre than lane one of the clockwise carriageway, a car making the journey in lane one anti-clockwise will travel about 500 feet less than one completing the journey clockwise.

Note that the distance the motorway is from the centre is not relevant to this calculation. The difference would be the same whether the M25 was one mile or a thousand miles from the centre.

[bednobs]

thanks all. For some reason i thought it would be in the order of miles

[factor-fiction]

This reminds me of the puzzle about the difference in lengths between a rope which goes around the equator resting on the earth's surface and another rope which is help up by sticks and goes around the world one metre above the surface.
Many expect the second rope to be significantly longer but, for the reason given by New Judge, the answer is around 6metres.

Anyway, to get back to the question, I'm confused. If they start at the same point in the same lane (so one goes the wrong way) then why don't they travel the same distance. Or if they both get on at Barnet (say) in the inside lane, and stay in that lane, but go in opposite directions, in theory wouldn't both cover exactly the same ground and distance?