BIG Dice Roll!

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RayZorback

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Jun 17, 2008
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What is the probability of rolling a 7 on a 120 sided dice? 1/120
What is the probability of rolling a 7 on a 120 sided dice out of 36 rolls? ____

How do you calculate this?

I'm not in school, I'm just curious because the numbers are in a game I play.
Thanks for the help!

EDIT: Please also explain the difference in "Expected Outcome" & "Probability". I think that is where I'm getting hung up.
 
The probability of NOT rolling a 7 in 36 rolls would be \(\displaystyle (\frac{119}{120})^{36}\approx{.74}\)

Therefore, the probability of rolling AT LEAST one seven would be \(\displaystyle 1-(\frac{119}{120})^{36}=.26\)

The probaility of rolling EXACTLY one 7 in 36 rolls would be \(\displaystyle 36(\frac{1}{120})(\frac{119}{120})^{35}\approx{.223}\)

Here is a curious one. What would be the probability of rolling all 7's out of 36 rolls. Intuitively, we know it would be astronomically low. \(\displaystyle (\frac{1}{120})^{36}=1.4108\times{10^{-75}}\)
 
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