Hilton Hotels Corp. reported its profit rose 22 percent in the third quarter partly because of improved results in its casino operations. Hilton said Wednesday it earned $27.2 million, or 57 cents a share, in the quarter ended Sept. 30, up from $22.3 million, or 44 cents a share, a year ago. Sales totaled $236.1 million, up 19 percent from $198.2 million a year earlier. Gambling revenue nearly doubled, jumping to $33.1 million from $18.5 million in the 1987 third quarter. The gain was partly due to better results at Hilton's Nevada casinos and to the company's interest in the Conrad International hotel-casino in Queensland, Australia. Operating revenue in the hotel sector declined 12 percent to $21 million. The drop was largely due to a one-time credit that boosted revenue in the 1987 quarter and a charge for taxes that depressed the figure for the latest quarter, said Roy Judge, a vice president and assistant to the chairman. Hilton said hotel occupancy increased to 71 percent, from 70 percent a year ago, while Nevada gaming occupancy reached 90 percent, against 83 percent in 1987. For the year to date, profit rose 17 percent to $95.7 million, or $1.99 a share, from $81.5 million, or $1.62 a share. Revenue in the nine-month period totaled $699.2 million, up 12 percent from $623.4 million.