Answer: (1) There are two quantities in the table, namely, the tonnage transported every day and the number of days transported, which are related quantities.

(2) (The answer is not unique) 300? 1=300, 150? 2=300, 100? 3=300, the products are equal, all are 300. Products represent the overall quality of goods.

(3) The relationship is inversely proportional, because the tonnage transported every day is changing, and the number of days transported is also changing, and their product is certain.