I am dumb. Please tell me how this works...

Message Bookmarked

Bookmark Removed

http://www.dslextreme.com/users/exstatica/psychic.swf

I know it's something maths-y, but as I failed maths nearly every year of high school, I can't for the life of me figure it out.

― papa november (papa november), Sunday, 30 January 2005 12:10 (twenty years ago)

...or at least talk about it.

― papa november (papa november), Sunday, 30 January 2005 12:18 (twenty years ago)

Well, it's mindblowing at first, but then note how the symbols change each time...

Also, your answer will always be a multiple of nine..

― mark grout (mark grout), Sunday, 30 January 2005 12:21 (twenty years ago)

I knew there was some kind of trick to it, being the non-believing-in-psychics type. Thanks for the hints.

― papa november (papa november), Sunday, 30 January 2005 12:22 (twenty years ago)

The chart changes to suit those multiples...

― Andrew (enneff), Sunday, 30 January 2005 12:53 (twenty years ago)

We had a thread on a similar page -- what it comes down to is that for any number, performing that operation will result in that number's base minus one (we use a base ten system, so they all result in nine, but it works in other bases, in binary, in hex, everything). The symbols and presentation are to distract you from the fact that the symbols for the multiples of nine all match (except 90 and 99 sometimes, because you can't get those as your result).

― Tep (ktepi), Sunday, 30 January 2005 12:56 (twenty years ago)

What's really sneaky is that it'll work whether or not you add the digits together of the sum of the digits, which is handy when you aren't limiting it to two-digit numbers -- i.e. for 97, 9+7 = 16, subtract 16 you have 81, a multiple of 9; subtract 1+6=7 instead, you have 90, also a multiple of 9. For 53821, subtract 5+3+8+2+1=19, you have 53802; subtract 1+9=10 instead, you have 53811; subtract 1+0=1, you have 53820. I'm not going to figure out if any of those is a multiple of 9, but if one of them is, all three are.

― Tep (ktepi), Sunday, 30 January 2005 13:07 (twenty years ago)

Cool.

I tried number 11 a few times. 1+1=2 2-11=9 and it didn't work. What's that all about?

― papa november (papa november), Sunday, 30 January 2005 13:37 (twenty years ago)

Actually, I think I fucked it up. Numbers make my head sleepy.

― papa november (papa november), Sunday, 30 January 2005 13:38 (twenty years ago)

for a number of 2 digits, say AB (where A is the first digit and B is the second)

(A x 10 + B) - (A + B) = 10A - A = 9A i.e. a multiple of 9 (always 9 times whatever the first digit is).

― ken c (ken c), Sunday, 30 January 2005 14:03 (twenty years ago)

Ah, I think I've finally grasped it. So all the multiples of 9 will always have the same symbol even thought the symbol itself may change each time. Yes?

― papa november (papa november), Sunday, 30 January 2005 14:07 (twenty years ago)

yup.

― m. (mitchlnw), Sunday, 30 January 2005 14:14 (twenty years ago)

Similar: HOW THE FUCK DOES THIS WORK

I thought there was another one but I can't find it

― beanz (beanz), Sunday, 30 January 2005 14:17 (twenty years ago)

You must be logged in to post. Please either login here, or if you are not registered, you may register here.