You were on the right track. Here are two ways to go about it.
• By definition of conditional probability,
Pr[A | B] = Pr[A and B] / Pr[B]
Out of the total 100 participants in the survey, there are 18 people that both have a positive attitude and are over 35, so
Pr[positive and over 35] = 18/100
Out of the 100 pariticipants, 40 are over 35, so
Pr[over 35] = 40/100
Then the conditional probability you want is (18/100) / (40/100) = 18/40 = 9/20.
• There are 40 people over 35 in the survey. You want the probability that someone randomly chosen from this group has a positive attitude, of which there are 18. Hence the probability is 18/40 = 9/20.
Answer:
50.75
Step-by-step explanation:
Answer:
10x² - 12
Step-by-step explanation:
4x² - 7 + 6x² - 5 (combine like terms)
10x² - 12
Answer:
20 possible arrangements
Step-by-step explanation:
A: Alice
B: Bob
C: Cindy
X: other student
All the possible arrangements are:
When Bob is in the first place
B A C X X
B A X C X
B A X X C
B X A C X
B X A X C
B X X A C
6 possible arrangements
When Bob is in the second place (notice that neither Alice nor Cindy can be before Bob)
X B A C X
X B A X C
X B X A C
3 possible arrangements
When Bob is in the third place
X X B A C
Only 1 possible arrangement.
Total arrangements when Bob is before Cindy: 10
If Cindy is before Bob the same situations are repeated, given another 10 arrangements. So, the total line up in which Alice is somewhere between Bob and Cindy are 20.
