For a 12 m high mast, the height of mast of model ship =9 cm=0.09m
For a 1 m high mast, the height of mast of model ship =0.09 m12
Therefore, the ratio of dimensions of model ship and actual ship =0.09 m12
For a 1 m long ship, length of model ship =0.09 m12
For a 28 m long ship, length of model ship =0.09 m12∗28=0.21m=21 cm