Logic Circuits And Equations Issue - Multiply Binary Number By 3 I am trying to build a logic circuit that multiplies any 4 digit binary number by 3.
I know that if I multiply/divide number by 2 it moves left/right the digits, but what I'm 
 doing with multiply by 3?


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*How to extract the equations that multiply the digits?

*I need to use a full adder?
I would like to get some advice. Thanks!
EDIT

I would like to get comments about my circuit of Multiplier 4 digits binary number by 3.


The easiest way I see is to note that $3n=2n+n$, so copy $n$, shift it one to the left, and add back to $n$
