Bg (sửa phân số cuối thành \(\frac{20}{57.61}\)
Ta có: C = \(\frac{40}{31.39}+\frac{35}{39.46}+\frac{30}{46.52}+\frac{25}{52.57}+\frac{20}{57.61}\)
=> C = \(\frac{5.8}{31.39}+\frac{5.7}{39.46}+\frac{5.6}{46.52}+\frac{5.5}{52.57}+\frac{5.4}{57.61}\)
=> C = \(5.\left(\frac{8}{31.39}+\frac{7}{39.46}+\frac{6}{46.52}+\frac{5}{52.57}+\frac{4}{57.61}\right)\)
=> C = \(5.\left(\frac{1}{31}-\frac{1}{39}+\frac{1}{39}-\frac{1}{46}+\frac{1}{46}-\frac{1}{52}+\frac{1}{52}-\frac{1}{57}+\frac{1}{57}-\frac{1}{61}\right)\)
=> C = \(5.\left(\frac{1}{31}-\frac{1}{61}\right)\)
=> C = \(5.\frac{30}{1891}\) (bắt đầu xấu)
=> C = \(\frac{150}{1891}\)(so ugly)
Vậy C = \(\frac{150}{1891}\)(kết thúc không có hậu)