Quandaries and Queries


Who is asking: Other
Level: Secondary

I know that the odds are a little less than 50% for either black or red comming up on a spin of the roullette wheel. My question is what are the odds of red or black comming up 7 times in a row?



Hi Joe,

There are two types of roulette wheels. Each type has 36 pockets numbers one to 36 and alternately coloured red and black. They also have a green pocket with the number 0 on it. The difference is that some wheels have an additional green pocket with 00 on it. I am going to assume that you are using a 38 hole pocket with a 0 and 00 pocket.

On such a wheel the probability that red comes up is 18/38 = 0.4737. Likewise the probability that black comes up is 0.4737. So, I am going to spin the wheel 7 times. What is the probability that I get red each time?

The probability is

0.4737 0.4737 0.4737 ··· 0.4737 = 0.47377 = 0.0054