Answer:
n is less than or equal to: 10
Step-by-step explanation:
10n+20=120
subtract 20
10n=100
divide by 10
n=10
I think number #29 is A but may be B and number #30 is C
Answer:
a) p=0.2
b) probability of passing is 0.01696
.
c) The expected value of correct questions is 1.2
Step-by-step explanation:
a) Since each question has 5 options, all of them equally likely, and only one correct answer, then the probability of having a correct answer is 1/5 = 0.2.
b) Let X be the number of correct answers. We will model this situation by considering X as a binomial random variable with a success probability of p=0.2 and having n=6 samples. We have the following for k=0,1,2,3,4,5,6
.
Recall that
In this case, the student passes if X is at least four correct questions, then

c)The expected value of a binomial random variable with parameters n and p is
. IN our case, n=6 and p =0.2. Then the expected value of correct answers is 
9x^2 + 18x + 9 = 5
9(x^2 + 2x +1) - 5 = 0
x^2 + 2x - 4 = 0
Then use the quadratic formula.
1/4(2x - 14) = 4....multiply both sides by 4
2x - 14 = 4 * 4
2x - 14 = 16
2x = 16 + 14
2x = 30
x = 30/2
x = 15 <==