Question

Ten thousand raffle tickets are sold. one first prize of$2000,4 second prizes of $800 each, and10 third prizes of$400 each are to be awarded, with all winners selected randomly. if you are given one ticket, what are your expected winnings?

Answer 1

From the information given:
Random wins      2000       800        400           0
Probabilities        1/10^4   4/10^4    10/10^4    9985/10^4
thus the expectation will be:
E(x)=[2000+4*800+4000+9985*0]/10^4
E(x)=9200/10000
E(x)=$0.92