Odds Probability

[Simon]

I'm having an argument with someone about this, but I can't work it out myself, so can hardly win this argument. If you back a 1/5 shot what should the probability of that bet winning be?

Can whoever answers this also explain why. Thanks.

 

[SlimChance]

100/1.2= 83.33%. That does not necessarily mean you will win 83% of the time because invariably the bookmakers will have built in a margin. I would say if you back 1/5 shots blindly you would win or expect to win on average around 80% of the time.