by Sexton Blake » Aug 15th, '06, 15:43
I will be delighted if you can point out that I'm being an innumerate dolt here and explain what boomingly obvious thing I'm missing. I really will.
This concerns Mentalivity. If the class will take out their RRTCMs and turn to page 186 they will see this trick. Or perhaps not, if they have a different edition to mine; it'll be in there somewhere, though. As it happens, it's also demonstrated on Paul Wilson's RRTCM DVD set (disc 4); a fact I'll refer to later. OK, now my problem is rather specific, so I'll have to go into some detail. I hope you won't think it's disclosure, however, due to the fact that - if you don't know the trick - my 'explanation' will be so dense as to be impenetrable. (Actually, it may well like that be even if you do know the trick.)
Right, jumping in at the middle, the two specs have chosen a number each (Spec One's between 1 and 10, and Spec Two's between 10 and 20), with Spec One using that number to select a card. You've done a little business, and the pack in now in your hand waiting to have cards dealt from it. Note the order here, it's important.
1) For the first time, you ask Spec One for his number. (RRTCM and Wilson both example '6'.)
2) You deal out that many cards (1 - 2- 3- 4 - 5 - 6) - pausing before turning the 6th (or whatever) card and asking Spec One what his card was.
3) Lawks! (Slightly.) His card isn't at that position.
4) For the first time, you ask Spec Two for his chosen number. (RRTCM examples '15', Wilson examples '16'.)
5) You continue dealing to this number (7 - 8 - 9 - etc.) , which everyone accepts you couldn't possibly have known before, and - Lawks#2! (Unarguably.) - Spec One's card is at the number chosen by Spec Two, even though neither knew the other's number and you didn't know either.
6) Men faint. Women cast themselves upon you.
The key to this trick, as both RRTCM and Wilson lay out, is that - after reaching Spec One's number - you ask Spec Two for theirs. Say these are 6 and 16: you '16 - 6 = 10' in your head, continue dealing to 10, perform the move, carry on until 16, and bada-bing bada-booms. Easy.
Except, what about if Spec One chose, say, '7', and Spec Two chose, say, '11'. Now, 11 - 7 = 4. Which means that, by the time you've dealt out Spec One's number, you've already gone too far to perform the move and are up a creek. This happens not only with 7 and 11, of course. It's likely to happen pretty frequently, because it'll occur whenever the equation STn - SOn = x produces a result where x < SOn.
There are ways to stumble around this - ask both Spec One and Spec Two for their numbers before you start dealing, for example. But that weakens the trick, and might still leave you having to perform the move at an awkward time. What really gets me is that both RRTCM and Wilson flatly state that you don't ask for Spec Two's number before you've dealt out Spec One's, and they never even mention the x < SOn problem. Moreoever, Wilson says that Mentalivity was one of the first tricks he ever learned - so surely he must have run into this situation in the past? This urges me to believe that there must be something I'm missing here. But, for the life of me, I can't see what it is. Just do the trick, exactly as laid out in RRTCM, but change Spec Two's number to 11 and you'll hit a wall, as far as I can see.
Please explain how I'm being a dolt.