Page 20 - Probability Demystified

CHAPTER 1 Basic Concepts 9

8. On a roulette wheel there are 38 sectors. Of these sectors, 18 are red,
18 are black, and 2 are green. When the wheel is spun, find the
probability that the ball will land on
a. Red.
b. Green.

9. A person has a penny, a nickel, a dime, a quarter, and a half-dollar
in his pocket. If a coin is selected at random, find the probability that
the coin is
a. A quarter.
b. A coin whose amount is greater than five cents.
c. A coin whose denomination ends in a zero.

10. Six women and three men are employed in a real estate office. If a person
is selected at random to get lunch for the group, find the probability
that the person is a man.

ANSWERS

1. The sample space is $1, $2, $5, $10, $20.
1
a. P($10) = .
5
3
b. P(bill greater than $2) = , since $5, $10, and $20 are greater
than $2. 5
0
c. P($50) = ¼ 0, since there is no $50 bill.
5
2
d. P(bill is odd) = , since $1 and $5 are odd denominational bills.
5
3
e. P(number is divisible by 5) = , since $5, $10, and $20 are
divisible by 5. 5

2. The sample space is 1, 2, 3, 4, 5, 6.
1
a. P(2) = , since there is only one 2 in the sample space.
6
4 2
b. P(number greater than 2) = ¼ , since there are 4 numbers in the
6 3
sample space greater than 2.