Probability of failure in Phase I = 50%, . phase II = 30% and phase III = 40%: So how many drugs will successfully

Question

A pharma company tests 100 drugs on human volunteers. Probability of failure in Phase I = 50%, . phase II = 30% and phase III = 40%: So how many drugs will successfully 

 

Need step by step explanation

Answer 1

Phase I 50 fail, 50 succeed 50% of 100

Phase II of the 50 who succeeded, 30% fail and 70% succeed. .7 x 50 = 35

Phase III 40% of the 35 fail and 60% succeed, .6 x 35 = 21

21 drugs will be successful if 100 are tested