"Can you tell me just how many steaks there are?" asked the woman, confused about the side of beef she wanted to buy. "Also, how much hamburger? In fact, how much of everything?"

Unfortunately, the customer who wants to save about 30 cents a pound of buying beef this way must know enough to answer these questions for himself. The whole side can be cut up into hamburger and steaks. Or it can go for large numbers of raosts, or a combination of the two. The roasts can be large, medium or small; the ground meat lean or fatty.

The process begins with the side itself, which looks nothing like a steer. The carcass has been trimmed of the "fifth quarter"-hide, head, innards, tallow and lower legs. (These are sold to leather and rendering plants and are considered an important side profit.) It comes out of the cooling and aging rooms on large hooks, each side with a fore and hind quarter.

The price of a side of beef is based on "hanging" weight, usually about half the live weight of the animal. All the hanging weight technically belongs to the consumer, but in practice a lot of it goes into the scrap-meat bin at the butcher shop. The scrap-meat loss depends upon the yield grade of the animal-ranked onthe scale of 1 to 5-and ranges from about 20 percent for a high-yield 1 or 2 to about 45 percent for a low-yield 5. Some people want the scrap meat. It consists of many good soup bones, lots of suet and a good deal of edible meat for dog food or soup.

What happens next depends upon the choice of abbatoir. At Manassass Frozen Foods, where they encourage customers to watch the process, it takes a butcher and two assistants about an hour to cut up a whole carcass.

The electric saws whirr loudly through large chunks of bone, slabs of fat are trimmed, and steaks head down the line. Under USDA inspection codes, the meat is wrapped in see-through cellophane, each package containing the inspection seal and label identifying the cut of meat. Each package is then flash-frozen.

The confused woman customer had asked for no pot roasts, plenty of steaks and very lean ground meat. Generally the chuck goes into pot roasts, but this beef was probably tender enough for traditional pot roasts in the oven. So the butcher put about half of the chuck into steaks and half into roasts. The customer got eight large steaks, each enough for two or three people, and 10 roasts, each weighing about three pounds.

The short ribs are usually difficult to use. In this case, they were stripped for stew meat. The bones went to the scrap pile. But the ribs can also go as two standing rib roasts, or eight single-serving prime ribs. The flank becomes either stew meat or a couple of lean steaks. This is also where the London broil comes from. The shank is generally trimmed of some meat which goes into stew or ground beef; and the lengthy bone, which can measure 18 inches long, is sliced up into meaty soup bones. Left whole, it can later serve as a pot roast for four or more, since there's a good deal of meat on it.

The hindquarter, which has all the gourmet cuts, consists of loin, tederloin, top, middle and bottom round and the brisket. The customer got eight sirloin, six porter-house, seven T-bone, one bottom round roast, two brisket, one eye of the round.

She also got 45 pounds of ground meat and 20 pounds of stew meat, and asked for the scraps back to get the most for her money. Out of 253-pound side of beef, she got 45 pounds of scrap-a loss of less than 20 percent.

This low is fairly, according to Manassas manager L. W. Harding. Commercially raised beef tends to be considerably more fatty than the kind of home-raised animal which the woman had bought.

"There arn't a lot of yield-5 animals," Harding said in reference to low-yield beef, "but there are even less yield-1, with 20 percent or less in loss."

When buying a side of beef, there are several ways to ensure that you get what you pay for. Ask if they have an unconditional satisfaction-guarantee policy. Ask to be taken into the aging chambers to see the hanging sides. Each side should be on two hooks, one for each quarter. Fore and hind quarters do not look alike: If the butcher shows you two hanging pieces of meat that look virtually identical, shop elsewhere. Also make sure the two quarters aren't cut up into large chunks and hanging on "meat trees."

"What some people will do," Harding warned, "is take several chunks of the cheaper parts of the animal and hang it together and say that's a side. One side is two quarters and should be sold that way."

Unless you buy beef directly from a local farm, make sure that the sides you get from a beef dealer are stamped with both yield and grade stamps. These stamps are put in place at the large packing houses that slaughter huge lots of beef and ship them out all over an area. Smaller abattoirs, where most locally grown beef is slaughtered, generally don't offer yield grades because of the high cost, but most areUSDA-inspected.

Once you know the yield-grade of the meat you plan on buying, compute your cost accordingly. If the side sells for $1.60 per pound and you get a yield-2 side (the most common yield sold), add about 30 percent for the loss in butchering. This makes the actual cost $2.06 per pound-still a reasonable price at a time when all-cuts average is $2.35. Prices of side beef are fluctuating widely right now and most dealers feel they will continue to rise.

"Buying side beef is an investment," Harding says. "It's expensive in the short run, but right now it's an investment that will pay off." CAPTION: Pictures, 1, 2, and 3, no caption