Given that probability of getting a heart attack before any drug = 0.80
Drug D1 reduces the probability of a heart attack by 35 %. Therefore, the probability of a patient getting heart attackafter he has taken D1
=(1−0.35)×0.80=0.52Drug D2 reduces the probability of a heart attack by 20 %. Therefore, the probability of a patient getting heart attackafter he has taken D2
=(1−0.20)×0.80=0.64It is given that both D1 and D2 work independently. Therefore, the probability of a patient getting heart attack after hehas taken both D1 and D2
=(1−0.35)×(1−0.20)×0.80=0.416A total of 100 patients have taken both the drugs whereas only 50-50 patients took drug D1 and D2.
Hence, the probability that the selected patient was given both the drug is
Therefore, we can say that option A is the correct answer.