In mathsi 'answered' this question where i didnt know what i was doing was just writing down random stuff and my line of 'working out' didnt even add up, but i still got the right answer (crazy luck) but i didnt get the marks :(
http://www.libertarian.co.uk/lapubs/histn/histn015.pdf
And just so you know, there is another 15,999 sites on google, so if this does not help you im sure one of them will :)