A sociologist, physicist and mathematician were on a train travelling through Wales when, in the first field they passed through they saw a lone black sheep. ‘Look’ says the sociologist ‘all the sheep in Wales are black.’ ‘You can’t say that’ says the physicist ‘the most you can deduce is that there is at least one black sheep in Wales.’ ‘You are both wrong’ says the mathematician ‘all you can say is, in a field in Wales is a sheep, one of whose sides is black.’

Two cows in a field in Scotland, ones working the other is on holiday, she’s the one with a wee calf.

Genuinely worked with a kid in the 70's who believed there were only 4 8th's in an inch because he counted the small 8th's indicators on a tape measure. Same apprentice went for the dinners and one lad asked for a meat and potato pie and if they didn't have one 'get me anything'. They didn't have one so he came back with 10 Benson and Hedges. I'm not making this up

Maths related I suppose but the way to employ an accountant used to be to ask them what 2 + 3 adds up to then employ the one that replies "what do you want it to be".

Engineering joke I suppose but how many thous in an inch. Reply was, I don't know there must be millions.

I know a special number which ends in 9. If I move the 9 to the front of the special number, then I get a new number which is exactly 4 times the special number. What is the special number?

Correct. Well done. You solved it quicker than me. It took me a couple of days I think. I heard it about 5 years ago and found it again on a scrap of paper in a drawer last night. I think it's incredible that it works and can be solved from just knowing the number 9 and 4.