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