= 27d567bc2d48d9f40e9ccc20ea370b15)
army1987 comments on Rationality Quotes June 2012 - Less Wrong
You are viewing a comment permalink. View the original post to see all comments and the full post content.
= 783df68a0f980790206b9ea87794c5b6)
Loading…= b715d02e85f7b3b4ae65ca3d3e450868)
Subscribe to RSS Feed
Powered by Reddit
= f037147d6e6c911a85753b9abdedda8d)
You are viewing a comment permalink. View the original post to see all comments and the full post content.
Comments (413)
I recall a math teacher in high school explaining that often, in the course of doing a proof, one simply gets stuck and doesn't know where to go next, and a good thing to do at that point is to switch to working backwards from the conclusion in the general direction of the premise; sometimes the two paths can be made to meet in the middle. Usually this results in a step the two paths join involving doing something completely mystifying, like dividing both sides of an equation by the square root of .78pi.
"Of course, someone is bound to ask why you did that," he continued. "So you look at them completely deadpan and reply 'Isn't it obvious?'"
I have forgotten everything I learned in that class. I remember that anecdote, though.
IIRC there was an xkcd about that, but I don't remember enough of it to search for it.
EDIT: It was the alt test of 759.
Note that xkcd 759 is about something subtly different: you work from both ends and then, when they don't meet in the middle, try to write the "solution" in such a way that whoever's marking it won't notice the jump.
I know someone who did that in an International Mathematical Olympiad. (He used an advanced variant of the technique, where you arrange for the jump to occur between two pages of your solution.) He got 6/7 for that solution, and the mark he lost was for something else. (Which was in fact correct, but you will appreciate that no one was inclined to complain about it.)
Is 759 the one you are thinking of? The alt-text seems to be relevant.
Yes.