Here's something I learned, if that's a go math text book the answers are always in the last couple pages of the book
Answer: - 0.28
Explanation:
1) Expected value: is the weighted average of the values, being the probabilities the weight.
That is: ∑ of prbability of event i × value of event i.
In this case: (probability of getting 2 or 12) × (+6) + (probability of gettin 3 or 11) × (+2) + (probability of any other sum) × (-1).
2) Sample space:
Sum Points awarded
1+ 1 = 2 +6
1 + 2 = 3 +2
1 + 3 = 4 -1
1 + 4 = 5 -1
1 + 5 = 6 -1
1 + 6 = 7 -1
2 + 1 = 3 +2
2 + 2 = 4 -1
2 + 3 = 5 -1
2 + 4 = 6 -1
2 + 5 = 7 -1
2 + 6 = 8 -1
3 + 1 = 4 -1
3 + 2 = 5 -1
3 + 3 = 6 -1
3 + 4 = 7 -1
3 + 5 = 8 -1
3 + 6 = 9 -1
4 + 1 = 5 -1
4 + 2 = 6 -1
4 + 3 = 7 -1
4 + 4 = 8 -1
4 + 5 = 9 -1
4 + 6 = 10 -1
5 + 1 = 6 -1
5 + 2 = 7 -1
5 + 3 = 8 -1
5 + 4 = 9 -1
5 + 5 = 10 -1
5 + 6 = 11 +2
6 + 1 = 7 -1
6 + 2 = 8 -1
6 + 3 = 9 -1
6 + 4 = 10 -1
6 + 5 = 11 +2
6 + 6 = 12 +6
2) Probabilities
From that, there is:
- 2/36 probabilities to earn + 6 points.
- 4/36 probabilites to earn + 2 points
- the rest, 30/36 probabilities to earn - 1 points
3) Expected value = (2/36)(+6) + (4/36) (+2) + (30/36) (-1) = - 0.28
The answer is above.
Additional note 1:
Additional note 2:
In the answer I filled in "0" at the place where "n" was. This is because the question tells us n=0
Given:
Karen earns $54.60 for working 6 hours.
Amount she earns varies directly with the number of hours she works.
She need to work to earn an additional $260.
To find:
Number of hours she need to work to earn an additional $260.
Solution:
Let the amount of earnings be A and number of hours be t.
According to question,
...(i)
where, k is constant of proportionality.
Karen earns $54.60 for working 6 hours.
Divide both sides by 6.
Put k=9.1 in (i).
Substitute A=260 in the above equation.
Divide both sides by 9.1.
Therefore, she need to work extra about 29 hours to earn an additional $260.
