math
posted by sabir .
In a group of 100 people 40 own a cat, 25 own a dog and 15 own a cat and a dog.
Find the probability that a person selected at random from the group:
a) owns a dog or a cat.
b) owns a dog or a cat, but not both
c) owns a dog, given that he owns a cat
d) does not own a cat, given that he owns a dog.

math 
Reiny
N(C or D) = N(C) + N(D)  N(C and D)
= 40 + 25  15 = 50
prob(C or D) = 50/100 = 1/2
N(Cat or Dog, not both) = 40 + 25  15 15 = 35
Prob(that event) = 35100 = 7/20
c)
Prob( A  B)  conditional prob
= Prob( A and B)/Prob(b)
prob(dog  cat) = prob(dog and cat)/prob(cat)
= (15/100)/(40/100) = 3/8
d)
prob(cat  dog) = prob(cat and dog)/prob(dog)
= (15/100) / (25/100) = 3/5
Respond to this Question
Similar Questions

Riddle
There are 14 legs in this group. There are 6 heads in this group. There are 12 ears in this group. There are 50 fingers in this group. There is 1 tail in this group. Who could be in this group? 
math
In a community of 416 people, each person owns a dog or a cat or both. If there are 316 dog owners and 280 cat owners, how many of the dog owners own no cat? 
Stats
The branch manager of an outlet of a nationwide chain of pet supply stores wants to study characteristics of her customers. In particular, she decides to focus on two variables: the amount of money spent by customers and whether the … 
math
in a group of 100 people, 40 own a cat, 25 own a dog and 15 own a cat and a dog. Find the probability that a person chosen at random a) owns a dog or a cat b) owns a dog or a cat, but not both c)owns a dog, given that he owns a cat … 
math
Mrs. Bollo's second grade class of thirty students conducted a pet ownership survey. Results of the survey indicate that 8 students own a cat, 15 students own a dog, and 5 students own both a cat and a dog. How many of the students … 
Math
In a group of 37 children, 14 had a dog, 20 had a cat, and 12 had both a dog and a cat. How many children had neither a dog nor a cat as a pet? 
Statistics
Siegel found that elderly people who owned dogs were less likely to pay visits to their doctors after upsetting events than were those who didn’t own pets. Similarly, consider the following hypothetical data. A sample of elderly … 
statistics
Siegel found that elderly people who owned dogs were less likely to pay visits to their doctors after upsetting events than were those who didn’t own pets. Similarly, consider the following hypothetical data. A sample of elderly … 
math
Mrs. Bollo's second grade class of thirty students conducted a pet ownership survey.results of the survey indicated that 8 students own a cat, 15 students own a dog and five students owned neither a cat or a dog. how many of the students … 
Statistics and
In a survey of 144 pet owners, 31 said they own a dog, and 91 said they own a cat. 14 said they own both a dog and a cat. How many owned neither a cat nor a dog?