PROBABILITY
PROBABILITY
Students should be able to:
find the probability of a simple event by counting
find the odds of the event
find the probability of a multi-stage experiment
using a tree diagram
use the Fundamental Counting Principle to determine
the number of outcomes
Problem set
1.
What is the probability of picking a month of the year at random that begins
with the letter “J”?
2.
Find the probability of selecting a state at random that begins with the letter
“A”?
3.
In the set S = { 1, 2, 3, 4, 5, 6, 7, 8, 9 }, find the probability of selecting a
prime number if a number was chosen at random?
4.
If a card is selected at random from an ordinary deck of playing cards, what
is the probability that the card is a king?
5.
A drawer contains six black socks, four brown socks, and two green socks.
Suppose on sock is drawn at random and it is equally likely that any of the
socks will be picked, find the probability that the sock is either black or
brown.
6.
If the student council has 15 members, 7 boys and 8 girls, what is the
probability that a boy will be selected president, if the president is chosen
at random?
7.
What is the probability of selecting a number that is divisible by 4 from the
following set; { 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36 }
8.
In problem 7, what is the probability of NOT picking a number divisible by
4?
Probability
1
9.
A golf course has eighteen holes, if 5 of them are water holes, what is the
probability that a person playing is on a water hole?
10. The lunch wagon has 4 tuna sandwiches, 5 egg salads, 2 ham, and 3 turkey
sandwiches. If you reached in at random to select a sandwich, what is the
probability of selecting tuna or egg salad sandwich?
11. A coin is flipped twice, what is the probability that 2 heads come up?
12. A coin is tossed in the air, and then a die is rolled. What is the probability of
getting a head and a 5? What is the probability of getting a tail and an even
number?
13. If Bob’s batting average is .300, what is the probability that he will get two
hits in a row?
14. A study of people with an MBA degree shows that it is reasonable to assign
a probability of .800 that such a person will have an annual salary in excess
of $30,000. Find the probability that such a person will earn $30,000 or less?
15. If the odds in favor of the red Sox winning the series is 2 to 5, find the
probability that they will win?
16. If the probability that it will rain tomorrow is .6, what are the odds it will
NOT rain?
17. On a trip a man took 3 suits, 2 ties, and 2 hats. How many different choices
of these items of clothing can he wear?
18. Any one of three trains will take Bill from his home to school, any one of
four elevators will carry him to his floor. How many possible choices of
transportation by train and elevator can he select?
19. A restaurant has 4 main courses, 3 desserts, and 5 drinks available for the
lunch special. How many different lunches made up of a main course,
dessert, and drink can one choose?
20. A girl has 5 dresses, 3 pairs of shoes, and 3 coats suitable for wear at work.
How many choices of outfits with these items are possible?
Probability
2
A bag contains 1 red marble, 2 blue marbles, 5 green marbles, and 4 yellow
marbles. Assuming each of the marbles has the same size and weight and
marbles are picked at random.
1.
What is the probability of picking a green marble, on the first try?
2.
What is the probability of picking a blue marble, on the first try?
3.
What is the probability of picking a yellow marble, on the first try?
4.
What is the probability of picking a red marble, on the first try?
5.
What is the probability of picking a black marble, on the first try?
6.
What is the probability of not picking a yellow marble?
7.
What is the probability of picking a red or green marble, on the first try?
8.
What is the probability of picking a marble, on the first try?
9.
What is the probability of picking a blue or yellow marble?
10. What is the probability of picking a blue marble, then picking a yellow
marble after you replace the blue?
11. What is the probability of picking a blue marble, then picking a yellow
marble without replacing the blue marble?
12. What is the probability of picking a blue marble and a yellow marble in any
order without replacing the first marble?
Probability
3
13. What is the probability of picking a blue or a red marble?
14. What is the probability of picking a blue marble, then picking a red marble
and picking a green marble without replacing either marble?
15. What is the probability of picking a yellow marble and rolling a “3” on a
six-sided die?
16. What is the probability of picking a yellow marble, then rolling an even
number on a six-sided die?
17. What is the probability of picking a blue marble and flipping a fair coin and
getting “tails”?
18. What is the probability flipping a fair coin twice and getting “heads” both times?
19. What is the probability flipping a fair coin three times and getting “heads” all
three times?
20. What is the probability flipping a fair coin four times and getting “heads” all
four times?
21. What is the probability flipping a fair coin three times and getting “tails” exactly
two times?
22. What is the probability flipping a fair coin four times and getting “tails” exactly
three times?
23. What is the probability of rolling a “7” on a pair of six-sided dice?
24. What is the probability of rolling a “5” on a pair of six sided dice?
Probability
4
25. What is the probability of rolling a sum of eight on a pair of six-sided dice?
26. What is the probability of rolling a sum that is a prime number on a pair of
six-sided dice?
27. What is the probability of rolling a “7” or “11” on a pair of six-sided dice?
28. What is the probability of rolling an “8” on a pair of six-sided dice, then getting
heads on the flip of a fair coin and then picking a blue marble out of the bag?
29. What is the probability of drawing an “ace” from a standard deck of playing
cards?
30. What is the probability of drawing an “spade” from a standard deck of playing
cards?
31. What is the probability of drawing “ the ace of spades” from a standard deck of
playing cards?
32. What is the probability of getting dealt a “Royal Flush” in a game of five-card
stud?
Probability
5