if the odds are 3.00 the sum would read
100/3 = 33.33 leaving 66.67
33.33/66.67 = .499 x 1000 = bet $500
if you price a horse at 2.50 and it comes up 3.50 ...nice overlay if it wins
I have this to say though if you know your win strike rate and you can achieve above it by 10 cents then you are getting a little value with it
But remember you must take the good with the bad ....cheers

Panna.
Most fulltime professionals multiple bet on X number of horses in the 1 race to make a profit whichever 1 wins.

Cheers.
darky.