1 inch represents 20 miles, therefore (1 inch)2 represents (20 miles)2. Therefore 12 inch2 represents 202 miles2. Therefore, 12 inch2 represents 202 miles2. Therefore 1 inch2 represents 400 miles2. Therefore, 1 square inch represents 400 square miles. Therefore, since 1600 square miles = 4 times 400 square miles, 4 square inches represents 1600 square miles. Edwin