Câu 3: Trang 80 sách giáo khoa (SGK) Toán tiếng Anh lớp 4It is planned to arrange 180 tons of goods...

To set up 180 tons of goods on railroad cars, the number of cars required depends on the carrying capacity of each car, which can be either 20 tons or 30 tons.

In conclusion, the answer to part a) is 9 cars are needed, and the answer to part b) is 6 cars are needed to transport 180 tons of goods.

Therefore, if each car can carry 20 tons of goods, 9 cars are needed, and if each car can carry 30 tons of goods, 6 cars are needed to transport 180 tons of goods.

b) If each car can carry 30 tons of goods, then the number of cars needed is 180 tons / 30 tons = 6 cars.

a) If each car can carry 20 tons of goods, then the number of cars needed is 180 tons / 20 tons = 9 cars.