Step-by-step explanation:
The probability at least one contracts the virus is the opposite (1 minus) the probability that none contracts the virus.
Using binomial probability:
P = nCr pʳ (1−p)ⁿ⁻ʳ
P(none) = ₅C₀ (0.9)⁰ (1−0.9)⁵⁻⁰
P(none) = (0.1)⁵
P(none) = 0.00001
P(at least one) = 1 − P(none)
P(at least one) = 1 − 0.00001
P(at least one) = 0.99999
There is a 99.999% probability that at least one of five individuals contracts the virus.