The Business & Finance section yesterday incorrectly stated the approximate purchase price of Drug Fair by Gray Drug Stores Inc. The price is $34 million. In a separate article, the 1980 operating revenues for Baltimore Gas and Electric Co. should have been stated in billions of dollars. thecorrect figure is $1.2 billion.

Gray Drug Stores Inc., a Cleveland-based drug and discount chain, will buy control of Drug Fair Inc. and merge the area's second-largest drug chain into its operations.

Officials of both companies announced yesterday that Gray had offered to pay $20 a share for the drug company's stock -- morethan twice as much as the $9 or so at which the stock has traded recently. At that price, the acquisition will cost Gray approximately $3.4 million.

Drug Fair announced last Friday that an unnamed company had proposed acquiring a 47 percent interest in the company from the Elsberg and Gerber families that founded the drug chain. Yesterday Drug Fair announced that it was accepting the offer.

Under the proposal, Gray would operate Drug Fair as a subsidiary under its own name and would retain Drug Fair personnel and management, at least initially.

Shareholders will be asked to approvethe agreement in a special meeting in March or April. The merger must receive two-thirds favorable vote to take effect.

The proposal unites two companies, both of which recently have had problems.

Gray, a company with $407 million insales last year and 181 drug stores, is heavily concentrated in the Midwest around Ohio. "They've recognized for a long time that they have to diversify because of their concentration in the Midwest, which has been hurt by recession," said Jeffrey S. Stein, an analyst for McDonald & Co.

Drug Fair, which has 175 drug stores in the District, Maryland, Virginia, Pennsylvania, Delaware and West Virginia, has had to contend with losses related to a chain of retail clothing stores which it divested last March and to more recent losses which it blamed on sharp competition and depressed economic conditions.

Gray said yesterday that it will get rid of its discount store operations which operate under the name Rink's. The stores will be sold to Cook United for an undisclosed amount of cash subject to the working out of a financing arrangement and other agreements.

The combination of the two operations should produce a drug store chain with sales slightly higher than People's Drug Stores Inc., the leading chain in this area. People's sales in 1979 were $441 million compared with Drug Fair sales of $262 million and sales by Gray's drug division of $195 million. Gray is moving into a highly competitive situation in this area where three major chains -- People's, Drug Fair and Dart -- contend for sales.

"Gray can hold its own in a competitive market," said Stein, the analyst. He noted that the Cleveland drug chain shares its hometown with Revco, the largest drug chain in the United States. Getting rid of the discount stores and taking on more drug operations should result in some elimination of duplication and overhead and in economies of scale, he said, adding "I think it's a positive development."

Milton E. Elsberg, president of Drug Fair, said that the families who control the chain "were prompted to accept the proposal of Gray Drugs because of our confidence in the management of that company and because of their intention to retain Drug Fair personnel to operate what will be the Drug Fair subsidiary of Gray Drugstores Inc."

Trading in Drug Fair stock was delayed by the American Stock Exchange pending the announcement yesterday morning. Trading resumed about 11 a.m., and the stock finished at 17 1/4. During the past 52 weeks, the stock's low has been 5 7/8, with its high the 14 3/8 it reached after the announcement Friday. More typically the stock has traded at around 9.