Harlene tosses two number cubes. If a sum of 8 or 12 comes up, she gets 9 points. If not, she loses 2 points. What is the expected value of the number of points for one roll?

A)-2/3
B)-1/6
C)1/6
D)2/3

Question

Harlene tosses two number cubes. If a sum of 8 or 12 comes up, she gets 9 points. If not, she loses 2 points. What is the expected value of the number of points for one roll?

A)-2/3
B)-1/6
C)1/6
D)2/3

anonymous · Answer

No idea, @e.mccormick might be able to help you. :)

campbell_st · Answer

well you need to multiply the probability by the payoff..

so what P( 8 or 12) = 

so how many ways can you get 8 from rolling 2 dice... and 12 occurs 1 way

you can use a table of tree diagram to get all the possibilities 

then its

Expected value = P( 8 or 12) x 9 + P(not 8 or 12) x -2

hope it helps