If you have two numbers,that are different ie,12 then you turn it round,21, take the lower number away from the higher number ,why does the answer always work out as 9 whatever two number you chose?
Question asked by: knowitall
This doesn't always work, for instance 33 reversed is 33.
If the difference between the digits is 1 then this works simply because of the non-trivial fact that x - y is (x - 10) + 1 therefore the reversal is mimicking this fact.
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