"Seventy-five point two percent,'' said the woman, shaking her head in disbelief. "Seventy-five point two percent ,'' she repeated, as her neighbors shook their heads sympathetically. none of them needed to be told that the woman was reciting the latest bad tidings from the D.C. government: a proposed increase in property assessment that will determine her taxes next year.

In a scene likely to be repeated in church basements and living rooms throughout the city in the coming weeks, the members of the 1500 T Street Block Council met last Thursday night in the chapel of Saints Paul and Augustine Church to formulate a collective "Ouch! '' to city officials. They hoped their group response would ring louder in official ears and result in a scaling down of this year's assessments.

"Well, when you feel like you've been run over by a steamroller, you've just got to get together," said Kay eckles, a member of the Block Council. Owner of her home at 1524 T St. NW, Eckles' assessment rose 35 percent, from about $59,000 to just under $80,000, she said. Eckles, 55 and retired, paid $516 in taxes last year, "double what I paid when I bought the house in 1973," she added.

The picture for 73-year-old Gertrude Blackistone was even bleaker. the proposed assessment on her home, at 1535 T St. NW, rose 76.2 percent, from $54,000 in fiscal year 1981, which ends in July, to $95,200 for next year. "It feels like everybody's trying to take advantage of you; you're retired, you're on a fixed income," said Blackistone, who has lived most of her life in the home of her parents bought in 1920. "It's all money, money, money, I'm sick of it," she said. Last year's tax bill came to $552.

Group action against the assessments are nothing new for the 1500 block of T Street NW. In 1977, the group went before the Board of Equalization and Review, saying that property values had been kept at a low level because of proximity to the 14 street corridor, scarred in the 1968 riots, and then suddenly had been pushed arbitrarily high. They won "nothing really," according to Nathaniel Hill, of 1521 T St. NW, president of the block council for the last 10 years. "But we got the satisfaction of having made our appeal together."

This time, the group hopes to be more successful. To prepare for the appeal, members invited Joann Clark, their neighborhood assessor from the Department of Finance and Revenue. Clark said increases in assessments are based on sales prices in an area, as well as any home improvements an owner has made.

To Prove her point, she passed around a list of recent sales prices on and near the block. Members of the block council "Oohed" and "Aahed" as they poured over the list of prices, ranging from $82,555 for a shell sold in October 1980 to a newly renovated home sold for $162,500 in 1979.

Diane Williams, director of the Housing office at Saints Paul and Augustine, organized the meeting and helped thr group practice filling out appeal forms. The group also asked Clkark to take several please back to her supervisors, including a request for a higher homestead exemption; a tax rate lower than last year's $1.54 per $100; and additional relief for senior citizen homeowners and those on fixed incomes.

The group, while anxious, was courteous to Clark, who will be making a number of similar appearances throughout her reporting area in the coming week. "I was surprised that they were so nice," Clark said at the end of the two-hour meeting. "I thought it would be worse -- but then again, next week, I've got Logan Circle."