Question

I'm not sure this is the right place, but:
I am supposed to, given a 4-bit adder, design logic that will represent the outputs in BCD (binary coded decimal). The carry output should not be included, thus there should only be 4 inputs in the circuit. We are only representing one BCD digit, so nothing above 9, though the adder will produce 0 to 15. I have no clue how to represent this in a truth table...