Answer:
200 meters
Explanation:
If the ratio is 5 inches to 20 meters that means for every 5 inches in the model there will be 20 meters on the real ship.
If the model is 50 inches long that means that there are 10 5 inch segments, multiply this 10 by the 20 meters in the ratio and you will get 200 meters as the final length for the ship.