EDIT: None of that multiplication rule crap should apply here, D'OH! I think this too is another case of the binomial probability; hence: [tex] X \sim Bin(10,0.5) [/tex] I must evaluate the cases where, n=10,20,50,100 Ah! The 70% comes into play for the probablity. I want probablity of greater than 70%, or for values of [tex] X \geq .7n [/tex] Problem a.) From the table, [tex] P(X \geq 7) = 1- 0.945 [/tex] So, [tex] P(X \geq 7) = [/tex]5.5% Not good chances! Part b.) [tex] P(X \geq 14) = 1- 0.979 [/tex] [tex] P(X \geq 7) = [/tex]2.1% Part c.) [tex] P(X \geq 35) = 1- 0.99870 [/tex] [tex] P(X \geq 7) = [/tex]0.13% Part d.) [tex] P(X \geq 70) = 1- 1[/tex] I begrudgingly made a quick for loop in matlab to calculate Binomial probablity values as high as n=100, with x =70 and p =.5, It spat out 1.000. So, The probability of getting a 70% and up is 1-1=0. You ant gota chance. My advice, don't guess on your exams, always cheat.