Fascinating – haven’t seen/done any of those for donkey’s (but I can say I did spot the deliberate error!). Laviticus has a good point. There’s all this stuff you do at school/uni and then never use in day to day work (unless you’re an engineer – mate of mine designs bridges and things like that). Of course there are two purposes to this education – other than to learn the specifics (eg. algebra) you’re being taught to think and reason.