1:Take any three digit number in which the first digit is larger than the last digit.
2:Reverse the number and subtract the smaller number from the larger one.
3:Reverse the result and add the number to the result.
4:The answer is 1,089 every damn time.

Can any math monsters out there please explain why this is so?
'cause I'd really like to know!

The answer is 1,089 every damn time. 312 - 213 = 99
99 reversed is 99
99 + 99 = 198
198 <> 1089

?

I dunno- try the number 725.the reverse of the number is 527. subtract 527 from 725 and you get 198. The reverse of the result is 891. Add this number to 198 and there's that rascally 1,809. If the result from step two is a two digit number, put a 0 in front before reversing it. Like if it's 99, make it 099--the reverse would be 990. Sorry for failing to mention that.

what is the secret of 1,089?

Originally posted by airdog
If the result from step two is a two digit number, put a 0 in front before reversing it. It's still only a two-digit number, so your theorem does not really hold true.

BUT! :D

If you insist on your most recent stipulation, the effect you are seeing is based on the 9's compliment property of base 10 math. Starting with any three digit number, provided that the number is different when it is reversed, when you find the difference between the two numbers you always end up with a number where the outer digits add to 9 and the middle digit is 9.

Therefore, the third step will always yield the answer of 1089.

Peace.


Is this homework??

G-fish, it ain't my theorum. But your reply does clear things up. Rock on.

Sorry, did not mean that as a possessive “your”.

And are you sure you get it? If so, you should be ready
to explain why adding the outer digits always results in 9.

:eek:

Nah, you just reminded me of other math-type riddles from a while back that had an explanation similar to the one you posted.
I'm only making entries because my neighbor's dog, Sam, tells me to.

lol, i hope i'm not the only one to get the david berkowitz reference....

:D

I just did 452, and it works: 452-254=198
198+891=1089 aka that same damn
number!

to the cat who just checked his #'s and deleted: see what I mean? It's more like a card trick, I guess, but in ancient times, (when our number characters were first used), somebody probably would've built a shrine to that same damn number...1089. My neighbor's dog, Sam, has assured me of this.

hey i wanna know about the dog and david b. (subway?)

berkowitz's neighbor had two sons who brought him into their little cult. their dog, a shepherd, was named sam. as berko went off the deep end, he said it was related to communications from the dog. maybe the old man's name was sam, as well. there's a truly hair-raising book on the story called "the ultimate evil," by a cat named maury terry. i read it years ago and it is scarier than michael jackson's (current) face.