[lancsdave]

Shall I be the spoilsport who posts the answers. I did know 2 & 3 because I worked for a civil engineering company years ago, but I had to look up number 1 so these are the answers from new scientist;

1 Cold. You could be at the North pole or in Antarctica, at a point 5 miles north of where the circle of Earth's latitude is 5 miles around. You could also be 5 miles north of any circle of latitude whose length is such that walking 5 miles along it takes you around a whole number of times

2 There's more than one answer, but the main one is that their shape means you can't drop them down the hole no matter which way you turn them

3 Plenty of possible answers, but one is that people disembark from trains in a surge, whereas those entering the station arrive in a steady trickle