If you want to know what is the probability that the coin will come up heads, then that would be: heads / (heads + tails) = 1/2 = . 5. Likewise when playing an even money bet at roulette, that option covers 18 of the 37 possible outcomes: 18/37=. 48648649.

The probability of a favourable outcome among all possibilities can be expressed: probability (p) equals the total number of favourable outcomes (f) divided by the total number of possibilities (t), or p = f/t.

Atmospheric conditions continually change and the wheel itself has features that encourage randomness  such as the size of the frets between the numbers and the diamond-shaped obstacles that intercept the ball as it falls down to the wheel. This means that you cannot predict the exact number where the ball will land.

In European Roulette, the RTP is 97.3% no matter what you bet. This means that for every 100 you stake, you can expect to get 97.3. Of course, in the short term, you can win anything from roulette because luck plays its part.