system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do horse racing odds work and why can some work out to 3-5, where you can only lose money?

I was watching the Preakness and saw that the horse Nyquist, who had won the Kentucky Derby had odds of 3-5. This seemed to mean that betting $5 would net a payout of $3. If so, why would anyone bet on that horse, even if the previous victory means they are more likely to win?
gpt
you almost have it correct, but you are forgetting an important part of the equation.  You always return the original bet.

So, with 3-5 odds, if you bet $5 to win, and the horse wins, you get back your original $5. Plus you get the $3 profit on the 3 for 5 part of the odds.  

So on a $5 bet that wins, you get back $8 at 3-5 odds.


Of course, such small payouts are unusual because it means a horse is expected to be much the best, but as we saw today, any horse can lose... today the track was deep and the early speed pushing Nyquist was too fast and took it's toll... he tried his guts out but tired late.