Question

In a die game, you roll a standard 6-sided die twice. If the second number rolled is the same as the first number rolled, you win $25. Otherwise, you lose $2. If you were to play the game 100 times, how much money can you expect to make

Answer 1

You can expect to make $250.

Explanation:

Possible outcomes:

For the pair of dice:

(1,1), (1,2), (1,3), (1,4), (1,5), (1,6)

(2,1), (2,2), (2,3), (2,4), (2,5), (2,6)

(3,1), (3,2), (3,3), (3,4), (3,5), (3,6)

(4,1), (4,2), (4,3), (4,4), (4,5), (4,6)

(5,1), (5,2), (5,3), (5,4), (5,5), (5,6)

(6,1), (6,2), (6,3), (6,4), (6,5), (6,6)

So 36 total outcomes.

Probability of the second number rolled being the same as the first number rolled:

6 outcomes: (1,1), (2,2), (3,3), (4,4), (5,5), (6,6)

Out of 36, thus:

`p = (6)/(36) = (1)/(6)`

Expected value of 1 game:

1/6 probability of earning $25.

5/6 probability of losing $2.

Thus:

`E = 25(1)/(6) - 2(5)/(6) = (25 - 10)/(6) = 2.5`

100 games:

100*2.5 = 250

You can expect to make $250.