find prob. of rolling exactly four 2's in five rolls of die

[lily06]

Rolling exactly 4 two's in 5 rolls of a die

I know it is probably easy, but I am trying to get this probability stuff down!

 

[tkhunny]

Pr(2) = p = 1/6
Pr(Not 2) = q = 1 - 1/6 = 5/6

Expand \(\displaystyle (p+q)^{5}\) and ponder its meaning.

After that, learn how to pick out the one you want.

 

[soroban]

Re: find prob. of rolling exactly four 2's in five rolls of

Hello, lily06!

Rolling exactly 4 two's in 5 rolls of a die

If you are familiar with the "Independent Trials" formula or "Binomial probabilities",

. . the answer is: \(\displaystyle \:{5\choose4}\,\left(\frac{1}{6}\right)^4\,\left(\frac{5}{6}\right)\)