Answer:
0.1296
Step-by-step explanation:
The desired probability is calculated by using geometric probability distribution having the pdf of
P(X=r)=p*q^r-1 where x=1,2,3,....
The geometric distribution is used because experiment is repeated various number of times until the success is obtained.
Here p is the probability of success which is 0.4 in the given scenario as Zach scores a ringer 40% percent of time
We wish to calculate the probability that Zach throws 555 or more to achieve his first ringer that is
P(R≥5)=1-P(R<5)=1-P(R≤4)
P(R≤4)=P(R=1)+P(R=2)+P(R=3)+P(R=4)
P(R≤4)=0.4*0.6^0+0.4*0.6^1+0.4*0.6^2+0.4*0.6^3
P(R≤4)=0.4+0.4*0.6+0.4*0.36+0.4*0.216
P(R≤4)=0.8704
P(R≥5)=1-P(R≤4)=1-0.8704=0.1296.
So it is 12.96% chance that the Zach throws 555 or more to achieve his first ringer.