In guinea pigs, smooth coat(S) is dominant over rough (s) and black coat (B) is dominant over white coat (b). In the cross SsBb x SsBb, how many of the offspring will have a smooth black coat on average

9/16

Explanation:

Smooth coat (S) is dominant over rough coat (s) and black coat (B) is dominant over white coat (b).

SsBb   x   SsBb

Offspring (You can also see the attached image for the Punnet's square analysis)

9 S_B_ = Smooth black coat

3 S_bb = smooth white coat

3 ssB_ = rough black coat

1 ssbb = rough white coat

Hence, on average, 9/16 of the offspring will have a smooth black coat