Statistics
posted by Lisa on .
1. In a certain game, the probability of getting a red outcome is 0.03. Find the probability of getting an outcome that is not red? The answer must be in a decimal.
I put 0.97 as the answer ( 10.03=0.97)
2. The instructor in a Humanities class says that students have a 15% probability of making an A in her class, 20% probabilty of making a B, 25% chance of making a C, and 20% chance of making a D. The possible grades that can be assigned are A, B, C, D, and F. What is the probability that a student does not make an A?
A) 50%
B) 70%
C) 85%
D) Cannot be determined from the information given.
3. The instructor in a Humanities class says that students have a 15% probability of making an A in her class, 20% probabilty of making a B, 25% chance of making a C, and 20% chance of making a D . The possible grades that can be assigned are A, B, C, D, and F.
What is the probability that a student does not make an A or a B?
A) 35%
B) 65%
C) 3%
D) Cannot be determined from the information given.
E) 20%
F) 15%
4. The instructor in a Humanities class says that students have a 15% probability of making an A in her class, 20% probabilty of making a B, 25% chance of making a C, and 20% chance of making a D. The possible grades that can be assigned are A, B, C, D, and F.
What is the probability of a grade more than a C?
A) 60%
B) 20%
C) 35%
D) Cannot be determined from the information given.
E) 40%
F) 65%
I don't know how to answer or set up problems 24...

your #1 is correct
#2. if prob(making A) = 15%
then prob(not making A) = 100%15% = 85%
#3. to make A or B = 15% + 20% = 35%
(since A and B are independent events, that is, you can't make both an A and a B), we can just add them up
so prob(not making A or B) = 10035 or 65%
#4 more than C  > either A or B which is 35% 
Thank you!