# Math Trick

## A Brain Teaser

Here is a trick I ran across and found interesting.

Think of a 3-digit number where the difference between the first and last digit is at least 2 (for example, 124 works, 122 does not).

Reverse the number and subtract the smaller from the larger.

Reverse this new number, and add it back to the result of Step obtained above.

70% of the time you will get 1089.

## I Tried this 10 Times and Got 1089 Each Time

## Give this a Try Yourself

As you can see from my numbers above, I tried this with ten different numbers and came up with 1089 as the result each time.

Try this yourself and let me know if you can find any numbers which are in the 30% that do not result in 1089.

Enjoy!

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## 13 comments

You are wrong. try this number 569. The result can't be 1089. Good try anyway! :)

at 12 noon the principal sent home 1/3 of the student plus 6.

at 1pm she sent home 1/4.

at 2pm she sent home the rest which was 21 how many did she start with???

I have known of this "trick" for over 20 years, but can't find anyone who can explain algabraicly why it works!

this is very cheap trick

nicE tricks....hehehe...Good Job...tnx

i cant understand your tricks.it is local

its not Interesting

its very easy to understand how

its like that i say 2+2=4

this one is easier....

find a 3 digit number then reverse it.ex.. 256->652...subtract to get 396 then reverse it again(693) then add...answer 1089....try it

Very Interesting

Hmm.. Is it not interesting that the number in Step 4 & 5 always turns out to be a 2-digit multiple of 9, with 9 separating the two digits?

18 --> 198

27 --> 297

36 --> 396

The middle number is always 9, while the outer two numbers make up a multiple of 9! Just thought I might point that out.

I checked this with a spreadsheet. If you consider the reverse of 99 to be 990, and the reverse of 100 to be 1, then every 3 digit number will yield 1089 unless the first and last digits are identical, in which case the result is 0. I'm not sure where the 70% comes from.

13