Solomon Hill added 18 points for Arizona (19-2, 7-2 Pac-12), which swept the Washington schools on the road.
Brock Motum and DaVonte Lacy each scored 15 points to lead Washington State (11-11, 2-7), which has lost four of its past five games. D.J. Shelton added 13 points and 10 rebounds.
Hill scored all his points in the first half, when Arizona built a commanding lead it never lost.
Mike Ladd, WSU's second best offensive weapon, picked up his second foul three minutes into the game and went to the bench. Arizona responded with an 11-2 run for an 18-9 lead.
Arizona's Kevin Parrom was ejected from the game with 10:42 left in the first for a flagrant foul on Lacy. Ten seconds later, Ladd was called for an intentional foul and Arizona cashed that in for two free throws by Brandon Ashley and then, when they received the ensuing possession, Hill nailed his third 3-pointer of the game for a 26-12 Arizona lead.
Motum's basket brought WSU within 26-18. Then, Hill hit his fourth and fifth 3-pointers of the first half as Arizona went on an 11-2 run for a 37-20 lead.
Washington State cut Arizona's lead to 11 points with a pair of 3-pointers. But Hill launched a buzzer beater from half court and it banked in for a 40-26 Arizona lead at halftime.
Hill made six of eight 3-pointers in the first, and Arizona shot 43 percent.
Washington State made just eight of 22 (36 percent) shots in the first half, and also had eight turnovers.
Washington State found its shooting touch early in the second half, but Ashley made three quick baskets to keep Arizona ahead 50-36. Then WSU went cold from the floor again and Arizona pulled away to a 57-38 lead with 11:54 left.
But Washington State wasn't done. Motum's basket launched an 11-3 WSU run that brought the Cougars within 60-49. Ashley fouled out after scoring 10 points, and Shelton's 3-pointer cut the Arizona lead to 10 at 64-54 with 4 minutes left.
Lyons sank a 3-pointer and a layup as Arizona pulled to a 71-56 lead, and Washington State was done.
Arizona leads the series 56-16. Meanwhile, Washington State has lost to all four ranked opponents it has played this season.
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