1 hinh thang co chieu cao la 10m hieu 2 day la 22m keo dai day nho = day lon de hinh da cho thanh hinh chu nhat co chieu dai = day lon chieu rong = duong cao hinh thang dien tich duoc mo rong them = 1/7 dien tich hinh thang cu 1 phan mo rong them co dien tich la 90m2