HAMBANTOTA: Upul Tharanga hit a century and paceman Lasith Malinga grabbed five wickets as Sri Lanka posted a crucial 78-run win over Australia in the third one-day international on Tuesday.Left-handed opener Tharanga made 111 for his 12th one-day hundred as Sri Lanka scored 286-9 before dismissing Australia for 208 in the must-win match, despite Michael Hussey's fighting 63Man of the-match Tharanga, playing his first series after serving a three-month drugs ban, also completed 4,000 runs in one-day internationals during his 139-ball knock, which contained 12 fours.Australia, who won the first two games of the five-match series, were struggling at 52-3 after debutant seamer Shaminda Eranga bowled Brad Haddin in his opening over and then held a return catch to dismiss Ricky Ponting (22).Skipper Michael Clarke (46) and Hussey steadied the innings with a 71-run stand for the fourth wicket before Malinga struck a vital blow.The Australian captain looked set for a third successive half-century before being caught by Mahela Jayawardene at mid-on. Malinga ensured the win when he dismissed Hussey to finish with 5-28, his fourth five-wicket haul.Sri Lanka were earlier strongly placed at 220-1 after 38 overs but paceman Doug Bollinger (4-42) bagged three wickets in two overs, including those of Tharanga and Kumar Sangakkara (49).The hosts made their best start in the series when Tharanga and Tillakaratne Dilshan (55) put on 139 for the first wicket in the day-night match, watched by Sri Lankan President Mahinda Rajapakse and his Maldivian counterpart Mohamed Nasheed.Jayawardene was the other main scorer with a 33-ball 36.The Australian bowlers, who set up their team's comfortable victories in previous games, had to wait for more than 25 overs for the first wicket.Bollinger provided the breakthrough when he had Dilshan caught pulling by Michael Hussey before Tharanga and Sangakkara added 81 in 13 overs for the second wicket.Sangakkara hit a 37-ball 49 before being trapped leg-before by Bollinger, who got his second wicket in the same over when he had Dinesh Chandimal caught by Clarke in the slips.Bollinger struck again when he had Tharanga caught behind in his next over.