Math CentralQuandaries & Queries


Question from Jerry:

while driving in my car early this morning, i 'discovered' something and want to ask if there is an equation that would fit it...
Here it goes..... take any two numbers (with the exception of two of the same numbers), multiply the first number by 2,
add the difference of the original two numbers, and the outcome will be the same as if you added the original two numbers together...
example: 3+5=8... thus, 3+3+(5-3)=8...
if you chose to reverse the numbers then..... 5+3=8... thus, 5+5-(5-3)=8

i know, simple stuff.. but i just want someone to tell me what exactly this is.. is there a 'law' that describes this?

please let me know... Jerry

Hi Jerry,

I think it is just algebra.
Suppose the numbers are x and y, where x is "the first" number.
Multiplying it by two gives you 2x.
The difference between the original two numbers (in reverse order) is y-x.
Adding this to 2x gives 2x + (y-x) = y+x = x+y, the sum of the original two numbers.


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