To answer problems like this you have to use binomial:
P (x > 1) = 1 – p (0
< x < 1) > .7
So:
1 – p (0) – p (1) >
.7
1 – (3/ 4) ^n – (3/ 4)
^n (n – 1 ) (1/ 4) > .7
Therefore n > 5.185,
and the smallest value of n so that we can satisfy the given condition is 6
(rounded up)
