sportingbet ou betfair

The payout odds for a bet on a single number is 35 to 1. This is odds of winning 1:35. This pays based on a probability of winning P_Win = A / (A + B) = 1 / (1 + 35) = 1/36 = 0.02778 or 2.778% (97.22% Losing). The true odds of winning are based on 38 outcomes.

When you see the odds presented as 30:1 or 3:1 that's actually just showing the payout for a winning bet, not the likelihood of that team winning. 30:1 doesn't mean that the team is 30x more likely to win, it means that if you bet on that team and they win you will receive $30 for every dollar you bet.