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Conditional Probability

Total questions: 8

Worksheet time: 10mins

Name
Class
Date
1.

This Venn diagram shows the results when 30 people were asked whether they have a cat or a dog.

Find the probability that a person selected at random has a cat given that they have a dog.

a)

79\frac{7}{9}

b)

1730\frac{17}{30}

c)

716\frac{7}{16}

d)

1726\frac{17}{26}

2.

The two way table shows information about the gender and age of employees at a company.

A person from the company is chosen at random. Find the probability that the person is female given that they are 30 or over.

a)

2857\frac{28}{57}

b)

1936\frac{19}{36}

c)

1928\frac{19}{28}

d)

2836\frac{28}{36}

3.

Lily has the following cards,

A A B B B C C D

Lily picks two cards. The first card is an A. Find the probability that the second card is also an A.

a)

17\frac{1}{7}

b)

28\frac{2}{8}

c)

18\frac{1}{8}

d)

27\frac{2}{7}

4.

A football team contains 9 boys and 6 girls.

The coach is choosing players at random for a match.

The first player picked is a boy.

Find the probability that the second player picked is a girl.

a)

615\frac{6}{15}

b)

68\frac{6}{8}

c)

614\frac{6}{14}

d)

814\frac{8}{14}

5.

Ben and Jacob randomly pick a packet of crisps from a multipack containing 6 packs of ready salted and 6 packs of cheese and onion. What is the probability they both pick a packet of ready salted crisps?

Give the answer in its simplest form.

a)

14\frac{1}{4}

b)

524\frac{5}{24}

c)

311\frac{3}{11}

d)

522\frac{5}{22}

6.

Fred is a golf player. The probability that Fred gets a hole in one on a dry day is 0.2 and the probability that Fred gets a hole in one on a rainy day is 0.1. Fred is going to play golf tomorrow.

 

The probability that it will be raining is 0.7.

Find the probability that Fred will get a hole in one.

a)

0.13

b)

0.14

c)

0.07

d)

0.3

7.

Vicky has a box of chocolates containing 5 white chocolates and 11 milk chocolates. Vicky eats one milk chocolate.

 

Find the probability that the next chocolate she picks is also a milk chocolate.

8.

There are 8 counters in a bag. Three of the counters are red and the rest are blue. A counter is chosen at random. It is not replaced. A second counter is chosen at random.

 

Calculate the probability that both counters are blue.