The probability that a student is not swimmer is 1/5.find the probability that out of 5 students (1) at least 4 are swimmers and (2)at most 3 are swimmers

Answer 1

prob(swim)=4/5
prob(not swim) = 1/5
prob(at least 4 swim)
= prob(4of5 swim)+prob(5of5 swim)
= C(5,4) (4/5)^4 (1/5) + (4/5)^5
= ....

#2
how does "at most 3 are swimmers" relate to what we just found ?

Answer 2

Multiply on both sides mat 1/5
()()())())

Answer 3

Multiply on both sides mat 1/5
P (x)=1/5

Answer 4

At most 3 are swimmer i didn't got these