Smith's Food & Drug Centers Inc. reports third-quarter net income of $8.6 million or 34 cents per share, up 19 percent over the $7.2 million or 29 cents per share reported in the same three months last year.

Income for the first 39 weeks totaled $25.3 million, up 34 percent over the $18.9 million earned in the same period in 1989.Third-quarter sales of $510 million compared to $432 million last year, an increase of 18 percent.

Net income per common share, diluted by additional shares issued in connection with last year's public offering, was $1 compared to 87 cents, an increase of 15 percent. Sales in comparable stores opened at least a full year were up 7 percent for the first 39 weeks of the year.

Smith's opened 11 new combination food and drug centers during the first 39 weeks, in Burley, Idaho; Sunset City, Bountiful, Salt Lake City, Sandy and Orem; two in Las Vegas.; Las Cruces, N.M.; and two in Phoenix.

Fifteen of what the company termed "obsolete, smaller stores" were closed during the period, including six stores in southwest Idaho. The company also converted two stores to warehouse-type supermarkets.