Each question is worth 4 points (100/25=4)
Therefore, when you divide 83 by 4, you get 20.75, as as he's aiming to get a B, this needs to be rounded up to 21.
Xio would need to get 21 questions right to get a B, hope this helps :)
R+s-t-(r-s+t)
=2s-t is the answer
People think this answer would be just =2s but I have verified with an online calculator and the answer that textbooks look for regarding this is 2s-t
You would assume you would go r-r and thats 0 so no r's
you would say s-(-s) makes it plus and theres 2s
and you would say -t -(+t) is -t
that's why the answer is 2s-t
At first I also did t-(+t) and thought it would be no t's but the answer is in fact 2s-t
Answer: I think its C
Step-by-step explanation:
Answer:
The best estimate of the number of times out of 39 that Ariana is on time to class is 27.
Step-by-step explanation:
For each class, there are only two possible outcomes. Either Ariana is on time, or she is not. The probability of Ariana being on time for a class is independent of other classes. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
Probability of exactly x sucesses on n repeated trials, with p probability.
The expected value of the binomial distribution is:

The probability that Ariana is on time for a given class is 69 percent.
This means that 
If there are 39 classes during the semester, what is the best estimate of the number of times out of 39 that Ariana is on time to class
This is E(X) when n = 39. So

Rounding
The best estimate of the number of times out of 39 that Ariana is on time to class is 27.