Logic Circuits And Equations Issue - Multiply Binary Number By 3

Question

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?

1. How to extract the equations that multiply the digits?

2. 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.

Answer 1

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 $n$