Answer:
C. 3.4
Step-by-step explanation:
We need to find expected value, which is essentially the value that we expect to get based on the amount of each "thing" at hand.
Here, we have 4 multiple-choice questions worth 3 points each and 2 true/false questions worth 1 point each. Each multiple-choice question has 5 possible answers, so the probability that you get that multiple-choice question correct is 1/5. Similarly, each true/false question has 2 possible answers, so the probability that you get that question right is 1/2.
Expected value, denoted by E(x), has the formula:
E(x) = ∑ xp(x), where x is the number of points you get per problem here and p(x) is the probability of getting the problem correct
E(x) = 4 * 3 * (1/5) + 2 * 1 * (1/2) = 12/5 + 1 = 17/5 = 3.4.
The answer is thus C.
Answer:
10 friends
Step-by-step explanation:
we know that
The formula of the sum is equal to
![sum=\frac{n}{2}[2a1+(n-1)d]](https://tex.z-dn.net/?f=sum%3D%5Cfrac%7Bn%7D%7B2%7D%5B2a1%2B%28n-1%29d%5D)
where
a1 is the first term
n is the number of terms (number of friends)
d is the common difference in the arithmetic sequence
In this problem we have
----> the common difference
substitute in the formula and solve for n
![275=\frac{n}{2}[2(5)+(n-1)(5)]](https://tex.z-dn.net/?f=275%3D%5Cfrac%7Bn%7D%7B2%7D%5B2%285%29%2B%28n-1%29%285%29%5D)
![550=n[10+5n-5]\\ \\550=10n+5n^{2} -5n\\ \\5n^{2}+5n-550=0](https://tex.z-dn.net/?f=550%3Dn%5B10%2B5n-5%5D%5C%5C%20%5C%5C550%3D10n%2B5n%5E%7B2%7D%20-5n%5C%5C%20%5C%5C5n%5E%7B2%7D%2B5n-550%3D0)
Solve the quadratic equation by graphing
The solution is n=10
see the attached figure
therefore
She had 10 friends who got stickers
Answer:
The answer is C!
Step-by-step explanation:
