The Washington Post Co. yesterday reported its third-quarter profits rose 23 percent to $15.1 million ($1.08 a share) from $12.3 million (86 cents) and revenue grew by 11 percent to $225 million from $202.9 million.

The Post company's newspaper, magazine and broadcasting divisions all posted revenue gains for the quarter and for the year so far.

For the first nine months of the year, Post company earnings were up 29 percent to $51.3 million ($3.63) from $39.8 million ($2.80) and revenue grew to $700.7 million from $623.5 million.

Advertising linage at The Washington Post was up 5 percent for the quarter and 8 percent for the first nine months of the year. Newspaper division revenue showed an 11 percent gain for the quarter and a 14 percent gain so far this year.

Newseek magazine's revenue rose 9 percent during both periods; Newsweek carried 571 pages of advertising during the quarter, up from 563 in the same period a year ago. The number of pages so far this year is 1,948, compared with 1,879 for the same period in 1983.

Post-Newsweek television stations showed a 14 percent increase in revenue for the quarter and a 16 percent gain for the year to date.

The company's share of earnings of affiliates produced a loss for the quarter of $800,000, compared with a $1 million loss in the third quarter of last year. So far this year, affiliated operations have produced a $6.6 million loss, compared with a gain of $500,000 in the same period a year ago. The company said the loss came from its SportsChannel cable TV operations and its cellular mobile telephone venture.