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. is my append operator

f(x,y)    = |x| . |y|
f(1,45)   = 145
f(233,10) = 23310
f(8,2)    = 82
f(0,1)    = 1

This is a trivially easy problem to solve in programming using string concatenation. However, I can't seem to think of a good way to do this using purely arithmetic operations.

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2 Answers 2


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  1. Take $log_{10}(b)$ and round down to find the number of digits $n$.
  2. multiply $a$ by $10^n$
  3. add $b$
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