Australia kept their faint Rugby World Cup quarter-final hopes alive after beating Portugal 34-14.Portugal struck first but the Wallabies took advantage of Pedro Bettencourt's sin-bin with three tries to put them ahead before Fraser McReight secured the much-needed bonus point.Australia's last eight hopes now depend on how Fiji fare against Portugal next weekend.Ben Donaldson's penalty put the first points on the board for Australia four minutes in, but Portugal scored the first try of the game as Bettencourt crossed in the corner with Samuel Marques converting.Bettencourt was then sin-binned, but Donaldson missed the subsequent penalty and the Wallabies then quickly responded with a try to retake the lead as Richie Arnold crossed, with Donaldson able to convert.With Portugal a man down, the tries came in quick succession for Australia from Dave Porecki and Angus Bell, with Donaldson adding the extras.Nicolas Martins thought he had pulled a try back for Portugal just before the break but it was chalked off thanks to Andrew Kellaway's tackle and Australia led 24-7 at half-time.McReight crossed six minutes into the second half to secure the bonus point the Wallabies needed to stay alive in the tournament, before Portugal had another try disallowed after Mike Tadjer lost control of the ball.There was danger for Australia as they were reduced to 13 when Matt Faessler and Samu Kerevi were sin-binned within two minutes of each other.Portugal took advantage as Rafael Simoes scored a converted try with 10 minutes to go, but Marika Koroibete added Australia's fifth try to finish the game off.