It's Derby Day! Message #1 Posted by Don Shepherd on 3 May 2008, 10:41 a.m.
In honor of the Kentucky Derby, and since it is held in my home town (Louisville, Kentucky, USA), here is a HP17bII+ solver equation to calculate the payoff price of a $2 ticket. You can use this equation to make sure that the racetrack is not ripping you off.
First of all, here is how a parimutual payoff amount is calculated. There are three pools: win, place, and show. The payoff amount of each pool is calculated separately. The total amount wagered in a pool is the gross pool. From this, a percentage, called the commission (this is the racetrack's profit), is subtracted, giving the net pool. The net pool is payed out to the winners. From the net pool, you subtract the amounts bet on "finishers". In the win pool, there is only one finisher; in the place pool, there are two; and in the show pool, there are three. This amount is divided by the number of betting interests (1, 2, or 3) resulting in the share amount. The payoff amount is then calculated as the (share + amount bet on this horse) / number of $2 tickets. This amount is then rounded down to the nearest dime.
Here is the 17bII+ solver formula. You supply:
comm  commission, like .15 for 15% (the track will tell you this percentage if you bother them enough)
pool  1, 2, or 3 for win, place, and show
this  amount bet on this horse
fin  amount bet on other finishers
nonfin  amount bet on nonfinishers
The formula then calculates the $2 payoff amount.
PAYOUT=IP((THIS+(((THIS+FIN+NONFIN)X
(1COMM)THISFIN)/POOL))
/(THIS/2)X10)/10
