Pakistan made 263-7 after being sent in to bat, having looked set to post a much bigger score at several stages. But the home side replied with 265-3, winning with 30 balls to spare.
After paceman Josh Hazlewood applied the brakes to a promising Pakistan innings with three wickets, skipper Smith and ODI debutant Peter Handscomb put on 183 for the third wicket in the chase to set their team on the path to victory.
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Pakistan coach Mickey Arthur could only rue the mistakes that helped Australia take a 2-1 lead in the five-match series.
"Our only chance of really exerting pressure was to take early wickets, and we nearly had that right," said Arthur. "And where we're at as a team, we just can't afford those little lapses, so very disappointing."
Handscomb was given a couple of lifelines by Paksitan and eventually made 82 from 84 balls, with the game safely in Australia's hands by the time he was dismissed and the Australia batsman admitted he had a lucky day.
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"I think I'm going to buy a lottery ticket tonight," said Handscomb, who was dismissed off a no-ball while on zero. "As I was walking off, I started to hear the crowd going nuts, and couldn't quite work out what was going on. So I looked up on the big screen and saw the no-ball."
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