Giant Food Inc. yesterday reported an 11.6 percent increase in profits and a 9 percent gain in sales volume for the fiscal year ended Feb. 23.

The Landover supermarket chain said net income for the year was $45.2 million ($3.05 cents a share) compared with $40.5 million ($2.77) in the previous year. Sales rose from $1.95 billion in the prior fiscal year to $2.1 billion.

The unaudited sales and earnings results produced a net income margin of 2.11 percent, or the equivalent of 2 cents earned on every sales dollar. The industry average is just over 1 percent. A year ago, Giant reported an income margin of 2.07 percent of sales.

Giant said it realized the sales gain without building any new stores last year and during a year when inflation for food purchased in supermarkets was estimated at 3 percent. In the meantime, officials added, earnings in the second and third quarters were depressed by a discount-pricing program that the company introduced in its 74-chain drug store division last June. But increases in sales volume in both the food and drug divisions produced higher earnings, Giant said.

Sixteen-week sales increased 9.4 percent, from $632.2 million to $691.8 million. Net income totaled $17.7 million ($1.19) compared with $14.7 million ($1.01) in the comparable period a year earlier.

CSX Corp. yesterday reported a 20 percent decline in first-quarter profits, the result of lower levels of coal-hauling on the railroad holding company's lines.

CSX said coal traffic was down 11 percent, because utilities were building up their coal inventories early in 1984 in anticipation of a coal miners' strike that did not occur. The company said coal traffic began to improve last month. Traffic in other commodities was about even in the first quarter with 1984 figures, CSX said.

The Richmond-based company said the fall-off in coal traffic was offset somewhat by better results in CSX's natural resources division, which includes a variety of oil and natural gas production operations.

For the quarter, CSX said it earned $92 million (61 cents a share), down from $115 million (79 cents) in 1984's first quarter. Revenue dipped 5 percent to $2 billion from $2.1 billion.

Meanwhile, International Bank, a Washington-based merchant bank, corporate holding company, insurance and real estate concern, said it lost $8.8 million in 1984 as a result of increased costs of operating its property-casualty insurance business. "It experienced the same underwriting problems as the entire property-casualty insurance industry -- extreme weather conditions, higher claims frequency and a greater number of catastrophe losses," said George Olmsted, the company's chairman. Olmsted said the company's other divisions improved their results in 1984.

The $8.8 million loss contrasted with a profit of $5.1 million (40 cents) in 1983. In the fourth quarter, the company lost $3.4 million, double its 1983 fourth-period loss of $1.7 million.