What is the probability that Jesse drew the number 7?

Question

Ten employees randomly drew from 10 cards that were numbered from 1 to 10 to determine which training session they will attend. Those who drew even numbers had a training session before lunch. Those who drew odd numbers had their training session after lunch. Jesse has his training session after lunch. What is the probability that Jesse drew the number 7?

Answer 1

Prob ( 7 | odd) = 

 

Prob (odd AND 7)/Prob(odd) =  <--- definition of conditional probability

 

Prob(7)*Prob(odd | 7)/Prob(odd)=  <---- they are DEPENDENT; cannot be 7 unless it is odd

 

(1/10)(1)/(1/2) =

 

(1/10)/(1/2)

 

= 2/10

 

= 1/5