UPSC NDA Math Model Paper 5

Let the events B1,~B2 and B3 be defined as:
B1: Children who were found coronavirus positive in the last week
B2: Adults who were found coronavirus positive in the last week
B3: Senior citizens who were found coronavirus positive in the last week Let the event E be 'The person tested coronavirus positive died'
⇒P(B1)=200∕1200=1∕6,P(B2)=400∕1200=1∕3 and P(B3)=600∕1200=1∕2
Similarly, P(E|B1)=0.01,P(E|B2)=0.03 and P(E|B3)=0.15(........ Given )
Here, we have to find the value of P(B3|E)
As we know that according to bayes' theorem: P(Ei|A)=

P(Ei)×P(A|Ei)

n ∑ i=1 P(Ei)×P(A|Ei)

, i=1,2,........,n
⇒P(B3|E)=

45

52