In gambling, how much should I bet to win a specific amount of money? I have a seemingly simple problem but I can't work it out. Say I start with a bank of £20 - I would like to work out how much I should bet take my bank to £25 (assuming a win).
In this case we'll assume odds of 2.00. Since the amount I want to win is £5 I could bet £5/2.00 = £2.50 however, if the bet won my final bank would be £22.50 and not £25.
Can anyone point out what I'm missing here?
Thanks,
Matt

Your mistake is that $£5:2.00=£5$ profit, not $£2.50$ as you say, so your bank would be at $£25.00$, as you wanted.
If the odds are $d$ and you make a stake of $s$, then your profit $p$ is:
$$p=s(d-1)$$
So for a profit of $p$, you should stake;
$$s=\frac p{d-1}$$
