The total mileage of expressways in a province is 1400km. If the subgrade width is 50m, how many square meters is the area of expressways in this province? How many square kilometers?
1400km * 50m = 1400000 * 50 = 70000000m2 = 7000 km2
1400km * 50m = 1400000 * 50 = 70000000m2 = 7000 km2