Question 866735
You use the formula


(n C k)*(p)^(k)*(1-p)^(n-k)



Note: n C k is found through the <a href="http://www.mathwords.com/c/combination_formula.htm">combination formula</a>



In this case,



n = 11 (sample size)
p = 0.2 (probability of success, in this case, probability of picking someone with green eyes)
k = 4 (number of exact successes you want)



So you'd have



(n C k)*(p)^(k)*(1-p)^(n-k)
(11 C 4)*(0.2)^(4)*(1-0.2)^(11-4)
0.1107296256



You would use a calculator to evaluate to get the last line shown above. That means we'd have a 0.1107296256*100 = 11.07296256% chance of picking exactly 4 people with green eyes.



So the answer is actually <font color="red">11%</font> (and not 40%)