United led 2-0 at halftime on goals from 17-year-old Mason Greenwood in the seventh minute and England striker Marcus Rashford, who was named man of the match, in the 27th. Paul Pogba's pass split the Leeds defense and Aaron Wan-Bissaka's first-time cross was prodded home by Greenwood to open the scoring.
Phil Jones, left unmarked on a corner kick, powered a header into the back of the net for the other second-half goal in the 51st minute.
"The squad is strong, today just shows we have strength in depth, young players coming through and pace up front," United manager Ole Gunnar Solskjaer said.
In its tour opener last Saturday, United beat the A-League's Perth Glory 2-0. The two matches attracted crowds of more than 110,000, including 55,274 for Wednesday's match at the new Perth Stadium.
Team officials said United striker Romelu Lukaku did not play Wednesday's match due to a training injury, while goalkeeper David De Gea was ill.
Juan Mata captained the side and Wan-Bissaka made his first start for United, which again made 11 changes at halftime.
Leeds, which plays in the second tier in England, moves to Sydney to play the A-League's Western Sydney Wanderers on Saturday.
Man United next plays Inter Milan at the National Stadium in Singapore on Saturday, then Tottenham at the Hongkou Stadium in Shanghai on July 25. It concludes its five-match preseason tour against AC Milan in Cardiff on Aug. 3.
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