I guess the depth and the width that is referred to by the parcel of land is the height and length of base, respectively. If so, the area would be equal to:
Area of triangle = 1/2*base*height
Area of triangle = 1/2*1 mile *1.5 miles = 0.75 mi²
Next, we convert this to acres through the conversion: 1 mi² = 640 acres
Area = 0.75 mi² * 640 acres/1 mi²
Area = 480 acres
