Given:
p=0.2
independent Bernoulli trials (green=success)
Need to find: probability that first three trials are failures, and the fourth one is a success.
Method: The conditions given fit the requirements of the geometric distribution, where for k failures before the first sucess
P(k)=(1-p)^k*p
=(1-0.2)^3*0.2
=0.8^3*0.2
=0.1024
