The probability that all marbles are yellow is
(7/20) (7/20) (7/20) = 343/8000
We are given
x = 2 and 3
u = 2.5
s = 0.5
Getting the z score
z = (2 - 2.5) / 0.5 and (3 - 2.5)/ 0.5
z = -1 and 1
The percentage is
1 - 0.1557 = 81.5%
.186915888
that is the answer
if I meant 2.675 divided by .5 it is 5.35
