If an event has a 1 in 9 chance (0.1111) of occuring, the chance of it occuring 3 times in a row is

9 * 9 * 9 = 729

For your 3rd fav to win three times in a row at 6/1 (0.1428), assumming a 100% market and 6/1 as the actual chance of the horse winning

(6 + 1) * (6 + 1) * (6 + 1) = 343

So yep your right it is that simple

__________________
Pixie

"It's worth remembering that profit isn't profit until it's spent off the racecourse." -- Crash