# Probability casino question

1. Oct 22, 2009

### rowdy3

When you give the Venetian casino in Las Vegas $5 for a bet on the number 7 in roulette, you have a 37/38 probability of losing$5 and you have a 1/38 probability of making a net gain of $175. There's a example close to this problem in my book and followed the steps. I made a table and did the following: I did$-5 x 37/38(.974) = -4.87
I did $5 x 1/38(.026) = + 0.13 = -4.74. The answer is -. 26 cents. What did I do wrong? 2. Oct 22, 2009 ### Mark44 ### Staff: Mentor Your second expected value should be 175*(1/38), which comes out to about$4.61.
-$4.87 +$4.61 = -\$.26,

Note that the answer is probably NOT -.26 cents, which would be a fraction of a penny.

3. Oct 23, 2009

Thanks.