I want to design a circuit that multiplies a number by 6 an input binary number using only 4bit full adders. I designed the combinational logic but couldn't do it with 4bit adders as i were asked in my exam. any help?
Given you only need to multiply by 6, rather than a variable, split up the calculations into simple operations.
6 in binary is
110 which means \$1\times4 + 1\times2 + 0\times1 = 4 + 2\$. So how could you calculate \$6\times a\$ simply?
Hint: How do you multiply a number by 2 using only addition?
So how do you calculation \$6\times a\$ using only adders?