Question 1194901
<font face="Times New Roman" size="+2">


The probability of getting a correct answer to any single question is one in five or 0.20. Each question is an independent trial.  Since the probability is constant for a number of independent trials, use the binomial distribution:


The probability of at least *[tex \Large k] successes in *[tex \Large n] trials is given by:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ P(k,n,p)\ =\ \sum_{r=k}^n\,{{n}\choose{r}}\(p\)^r\(1\,-\,p\)^{n-r}]

Plug in the numbers and do the arithmetic.  You should get an answer that is smaller than 0.0009.

																
John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
My calculator said it, I believe it, that settles it
*[illustration darwinfish.jpg]

From <https://www.algebra.com/cgi-bin/upload-illustration.mpl> 
I > Ø
*[tex \Large \ \
*[tex \LARGE \ \ \ \ \ \ \ \ \ \  
								
{{n}\choose{r}}
</font>