I apologise for my poor construction here, I certainly did not want to imply that I actually encourage my students to look for mistakes! I did reference my concern about the dangers of encouraging arrogance in students by this approach in my post 62. I also tried to soften the blow with my use of the word "wary", but this still did not work! My main point remains, however, that errors in the printed word do occur, and we must all learn to deal with them, without being too critical of the persons who make them, which is what seems to have mostly occurred in this thread, prompting me to make my first post. Spending an inordinate amount of time on one question in an examination is anathema to me, and any student who does this has not learnt the most elementary of examination techniques, and gets little if any sympathy from me. I mark what they have done, fairly and without prejudice across the board, assuming that they are well-schooled in doing their best to impress me with their comprehensive/broad knowledge of mathematics, in the time available. Imagine expecting to pass one's driving test by spending an inordinate amount of time trying to show that you are capable of reversing into a nearside side road! I do not think the examiner would be impressed. I guess after the second attempt the examiner would tell us to move on!