A woman who signs herself "Hooked on Horses" has sent me a clipping of Jack Anderson's column for May 9 of this year and has enclosed this note:

"In this column, Anderson quoted Jimmy the Greek's odds on presidential aspirants. The Greek said Carter was 4 to 5, Kennedy 7 to 5, Brown 12 to 1, and Mondale, Moynihan, Byrd, Church, Udall and Califano were all 20 to 1. On the Republican side, he quoted 6 to 5 on Regan, 3 to 1 on Connally, 7 to 1 on Baker, 10 to 1 on Bush, 15 to 1 on Ford or Crane, and 50 to 1 on Thompson, Dole, Weiker, Laxalt, Anderson or Kemp.

"I realize that odds offered by bookmakers are always designed to give the bookie an edge, but I have never been able to figure out how big that edge is. I have been trying to calculate the house percentage built into Jimmy's odds ever since thay appeared, but have been unsuccessful. Can you tell me what percentage of profit a bookmaker will retain on this odds package?"

I doubt that the answer I give you will pass muster with mathematicians, but it may be close enough to make one fundamental point: Odds offered by a bookmaker are never generous enough to account for all the money that is bet. Enough is skimmed from the pool to guarantee a profit for the bookie, regardless of who wins.

Here's my do-it-yourself method for figuring out how much is being skimmed:

Add 1 to the odds quoted, then divide the sum into 100. This gives you the amount of money that should have been bet at those odds. Example: If the odds are 19 to 1, add 1 to 19, which gives you 20, then divide 20 into 100 and you will find that $5 should have been wagered to justify odds of 19 to 1.

To prove the arithmetic, subtract the $5 in winning bets from $100, and this leaves $95 available to pay off $5 worth of winning bets at 19 to 1.

Therefore: If Carter is 4 to 5 (.8 to 1), add 1 to .8, then divide 1.8 into 100. You find that $55.56 must have been bet on the 4-to-5 choice, leaving $44.44 in the pool to pay off the winners at 4 to 5. tSimilarly, odds of 7-to-5 (1.4 to 1) plus 1 cause you to divide 2.4 into 100, and you find that $41.67 was bet at 7 to 5. Odds of 12 to 1 indicate bets totaling $7.69, and the six 20-to-1 entries indicate that $4.76 was wagered on each, or a total of $28.56 on all six.

The total amount in the wagering pool is $133.48.The amount the bookmaker will pay out is $100. So the bookmaker will keep as profit approximately 25 percent of the money that is wagered with him. If you calculate the Republican odds quoted by the Greek, I think you will find that the total amount wagered is $133.10. So the bookie's profit remains constant.

If his "handle" on a game is $40,000, his profit will be $10,000. Or possibly more. When the winner turns out to be "none of the above" -- a dark horse on whom there were no bets -- the bookie keeps all the money.

It boils down to this: If there were 20 contestants and $5 was bet on each, the true odds on each entry would be 19 to 1. But a bookmaker would offer only 14 to 1 on each, assuring himself of a 25 percent profit. He would take in $100 and pay out only $70 plus the winner's own $5.

My arithmetic may be off a bit, madam, but I think it's close enough.

If you apply my calculations to the charts of races run at Maryland tracks, you will find that about 19 percent is skimmed from every mutuel pool.

Therefore, if a player makes 17 bets (nine races plus eight "exotic" bets) and loses 19 cents of each dollar he has wagered, by the end of the day he will probably have lost 3.23 times the amount of his average bet. That's why horse players die broke.

Some bookmakers also die broke, but those who do can be considered members of one of our smallest minority groups. SMILE A WHILE

Recent issues of Changing Times, the Kiplinger magazine, have offered some bright observations on the passing scene. Try these samples on for size:

"Junior has just doubled the value of his jalopy by filling the tank."

"Let's give the deep-slit skirt its due. It's a noticeable stride toward full disclosure."

"So far, the only gas conservation plan that really works is the Weather Service's. Rainy weekends."

"What this country needs is a car that runs on direct mail advertising."

"A double horror show is playing at the shopping center theater -- a scary movie on the screen and $1 popcorn in the lobby."

There's also a cartoon showing Arabs lined up at an oasis refreshment stand. A sign says, "Coke $2, Limit 3 Bottles." HOW TRUE, HOW TRUE!

Comedian Danny Klayman writes, "Those two Russian cosmonauts stayed together longer than most of today's newlyweds."