A Business section story Wednesday misstated American Management Systems Inc. profits for the first nine months of 1986. Profits were $3.5 million for that period and $4.2 million for the same period this year. (Published 10/23/87)

The Washington Post Co. yesterday reported third-quarter profits of $61.3 million, or $4.77 a share, almost triple the $21.1 million ($1.65 a share) earnings for the third quarter a year earlier.

Revenue in the quarter was $312.9 million, a 7.3 percent increase from the $291.5 million of the third quarter in 1986.

Included in third-quarter income this year were gains of $24.2 million ($1.88) from the sale of the company's interest in Detroit Cellular Telephone Co. and $6.1 million (47 cents) from the sale of The Washington Post's interests in four SportsChannel cable programming networks. Excluding these nonrecurring gains, third-quarter net income rose 47 percent to $31.1 million.

An after-tax gain of about $22 million from the sale of the company's interest in the Washington-Baltimore cellular telephone system will be included in the fourth-quarter results.

For the first three quarters of 1987, the company's income was $122.3 million ($9.51), up from $63.9 million ($4.98) a year earlier. Excluding the nonrecurring gains, profits rose 43.3 percent to $91.6 million ($7.12).

Revenue for the nine months was $950.4 million, up 7.8 percent from the $881.6 million of a year before.

Newspaper division revenue rose 8 percent in the third quarter of 1987 and 9 percent in the first three quarters of this year. Revenue for Newsweek, which is owned by The Post Co., was even with the previous year for both the quarter and the nine months.

Post-Newsweek television revenue was down 2 percent in the third quarter, but up 4 percent for the first three quarters. Cable division revenue rose 17 percent in the third quarter and 16 percent in the first three quarters.

Dyncorp yesterday reported profits for the third quarter ending Oct. 1 of $3.4 million (32 cents) on revenue of $220.9 million, compared with profits of $3.8 million (35 cents) on revenue of $186.9 million during the same period last year.

The McLean technological services company reported earnings for the nine months of $4.8 million (44 cents) on revenue of $634.3 million, compared with profits of $7.3 million (69 cents) on revenue of $535.1 million during the same period last year.

The nine-month figures include extraordinary charges of $3.5 million, including reserves related to a subsidiary's antitrust conviction and associated litigation.

Signet Banking Corp. reported net income of $24.1 million (92 cents) for the third quarter ended Sept. 30, up from $22.7 million (91 cents) for the same period last year.

For the nine months, net income was $6.0 million (20 cents) compared with $62.7 million ($2.58) for the same period last year. Signet's nonperforming assets totaled $167.1 million on Sept. 30 compared with $59.0 million last year. On June 30, nonperforming assets were $176.6 million. The higher level of nonperforming assets this year resulted from placing loans to Brazil and Ecuador on a nonaccrual status in March.

American Management Systems Inc. reported that net income for the third quarter ending Sept. 30 increased 24 percent, to $1.9 million (18 cents), from $1.5 million (14 cents) a year earlier.

Revenue rose to $44.7 million in the quarter from $28.0 million for the same period last year.

For the nine months, AMS said net income was $4.2 million (41 cents), down from $10.3 million (34 cents) a year earlier. Revenue was $102.3 million, up from $77.2 million.

Per share figures reflect a 2-for-1 stock split June 10.