probability formula used to find expected value of ticket

[Mary Jane]

Ten thousand raffle tickets are sold, and there is one first prize worth $20,000, one second prize worth $2500 and 20 third prizes worth $500 each. Find the expected value of a ticket. Which probability formula did you use?

 

[galactus]

What's the ticket price?.

 

[pka]

First prize probability is 1/(10000)
Second prize probability is 1/(9999)
Third prize probability is 20/9998.
NO prize probability is 1-[22/10000].
Expected value: [1/(10000)](20000)]+[1/(9999)](2500)]+[( 20/9998)(500)]-[P(1-[22/10000])]
This is where P is the price of a ticket.