I heard an interview with a human calculator over the weekend, this stuff interests me greatly, but I will assume that most of you will be bored out of your mind. I will not be mad if you skip this post entirely in fact.
Anyway, the guy was saying that one day he had an epiphany in that all numbers end up at nine. He gave some examples and it was very interesting. He showed how to check your math easily and how you can always be certain of your answers. Here is how:
If you are adding single digit numbers, such as 1 + 1, it is simple to check your answer.
1 + 1 = 2
You would take the 1 and the 1, put them together and you get 11.
Subtract your answer of 2:
11 -– 2 = 9
You end up with 9 so you know your answer is correct.
You can do this with any single digit addition with a twist, just make sure to add the answer together to get your 9. Like so:
5 + 4 = 9
54 -– 9 = 45
4 + 5 = 9!
With double-digit addition it is slightly different. You use your answer to figure it out to 9. Like so:
61 + 61 = 122
122 = 1 + 2 + 2 = 5
122 -– 5 = 117
117 = 1 + 1 + 7 = 9!
Sure, this has no practical value, but it amazes me, letÂ’s try one more before moving on:
52 + 89 = 141
141 = 1 + 4 + 1 = 6
141 - 6 = 135
135 = 1 + 3 + 5 = 9!
Now onto triple digits:
122 + 135 = 257
257 = 2 + 5 + 7 = 14
257 -– 14 = 243
2 + 4 + 3 = 9!
As you can see, everything is normal when your answer has three between 1 and 3 digits, letÂ’s get some 4-digit answer and see what occurs:
555 + 666 = 1221
1221 = 1 + 2 + 2 + 1 = 6
1221 -– 6 = 1215
1 + 2 + 1 + 5 = 9!
I donÂ’t know why this works, but it does, it doesnÂ’t seem to have any real value, but it really is amazing.
1356 + 8457 = 9813
9813 = 9 + 8 + 1 + 3 = 21
9813 -– 21 = 9792
9 + 7 + 9 + 2 = 27
This is the weird part, sometimes the answers are multiples of 9. But it is still 9 in the end!
55555 + 66666 = 122,221
1 + 2 + 2 + 2 + 2 + 1 = 10
122,221 -– 10 = 122,211
1 + 2 + 2 + 2 + 1 + 1 = 9!!
Well, there you go, I have fully exposed the fact that I am a numbers geek. All of the equations I have done in my head or on paper just about always end up at 9, and sometimes they end up at 27, a multiple of 9. If you find an equation that doesnÂ’t hold to this, please post it, I would be interested in seeing it.
You do know that no one is still reading this now, right?
3 comments:
Did this occur to you?
2+7=9
:-D
In fact, if I recall correctly, the digits of all multiples of 9 add up to 9...
I can't believe I missed that.....
Glad at least one other person found it interesting :)
Oooh! A way to play with numbers that has no real value, but is extrememly cool? This is even better than mentally doubling numbers until they're too big to remember.
Of course once you get beyond single digits it has nothing to do with the addition anymore. It works just as well if you skip the first step and pick a random number...
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