A commanding century from Aaron Finch (153) and a dominant showing from Mitchell Starc and Kane Richardson saw Australia beat Sri Lanka by 87 runs at The Oval here on Saturday. Chasing 338 to win, Sri Lanka started the run chase well but a collapse in the middle order meant Australia won their fourth game of the group stages and went on top of the standings. A 115-run opening stand between Dimuth Karunaratne and Kusal Perera gave the Lankans exactly the kind of platform they needed. Perara was cleaned up by Starc and Lahiru Thirimanne got a decent start but fell when he edged one to Alex Carey of Jason Behrendorff. Arguably the killer blow was struck when Karunaratne went for a cut shot off Richardson but only found Glenn Maxwell at point, the dismissal triggering a middle-order collapse. From 186-3, Sri Lanka lost 7 wickets for 61 runs and were bundled out for 247.Angelo Mathews, Milinda Siriwardana and Thisara Perera departed cheaply. Kusal Mendis also fell soon thereafter, holing out to David Warner off Starc. Isuru Udana and Lasith Malinga were both accounted for by Richardson and Pat Cummins – who had dismissed Mathews by getting him to edge one to Carey – got rid of Nuwan Pradeep in similar fashion to end the match. Earlier, Australia captain Finch equalled his highest ODi score of 153 as he powered the defending champions to 334-7. Finch took the misfiring Sri Lanka attack apart with a dazzling display that included 15 fours and 5 sixes. It was his 14th ODI century and the second of his World Cup career. The 32-year-old’s 132-ball knock took him level with his previous best score of 153 against Pakistan in March. Finch was well-supported by Steve Smith’s 73 from 59 balls and the pair put on 173 runs for the third wicket to set Sri Lanka a formidable total. Together with opening partner Warner, Finch took the attack to the Sri Lankans after being put in to bat and the pair passed fifty for the opening wicket for the fourth time in five games at the World Cup.Warner was the first Australian to perish when he was bowled by Dhananjaya de Silva for 26. De Silva struck again when Usman Khawaja (10) played a loose shot straight down the throat of Udana at deep square leg. That brought Smith to the crease and despite a few boos from the crowd, he continued his good showing the bat and his composed presence freed Finch to go for broke. Finch stepped on the gas to take 20 runs, including two sixes, off De Silva’s eighth over and he brought up his hundred with a six off Siriwardana. Sri Lanka had no answer to his brutal assault and by the time he departed, caught by Karunaratne off Udana, he had put Australia in a commanding position. Glenn Maxwell’s quick-fire 46 ensured Australia comfortably got past the 300-run mark despite a late collapse triggered by Udana’s double run-out of his own bowling towards the end of the innings.