Bedsit said:

The more numbers you cover the less chance you have of winning.

This is not true. You may win less, but the

**chance of winning** increases, the more numbers you bet.

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Now about the house advantage and expected value, which is a totally different concept than the chance of winning. Please go here:

http://www.roulette30.com/expected-valueYou will see that the appropriate way to calculate the house edge is this equation:

If you do the math you will find that the house edge is always -2,7%. The bet doesn't matter. Only your bet amount matters.