Simple Probability Worksheets

Simple Probability Worksheets
• Page 1
1.
A football manufacturer checks 400 footballs and finds that 8 balls are defective. Find the probability that the ball chosen is a defective ball.
 a. 2% b. 3% c. 20% d. 41%

Solution:

Number of favorable outcomes = Number of defective balls = 8

Number of possible outcomes = Total number of footballs = 400

= 0.02 x 100 = 2%
P(defective football) = number of defective balls / total number of balls = 8 / 400 = 0.02
[Substitute and simplify.]
[Multiply by 100 to write the decimal in percent form.]

The probability that the ball chosen is a defective ball is 2%.

2.
A basketball player attempts 50 baskets and makes 5. What is the probability of the player making a basket?
 a. 0.25 b. 0.1 c. 0.05 d. 0.4

Solution:

Number of favorable outcomes = number of baskets the player makes = 5

Number of possible outcomes = total number of attempts = 50

P(making a basket) = number of baskets / total number of attempts = 5 / 50 = 0.1
[Substitute and simplify.]

The probability of the player making a basket is 0.1.

3.
What are the odds in favor of the coin falling in the shaded region?

 a. 1 : 2 b. 1 : 3 c. 1: 1 d. 1 : 4

Solution:

Odds in favor of an event = number of favorable outcomes / number of unfavorable outcomes.

Number of favorable outcomes = 4

Number of unfavorable outcomes = 4

Odds in favor of the coin falling in the shaded region = 4 / 4 = 1 : 1

4.
The probabilities of John or Paula winning a game are shown in the pie chart. Is this a fair game?

 a. Unfair b. Fair

Solution:

P (John winning the game) = 0.6

P (Paula winning the game) = 0.4

Each player has different probability of winning the game.

So, the game is unfair game.

5.
Find P(not red), if P(red) is 31%.
 a. 31% b. 19% c. 69%

Solution:

P (red) = 31% = 0.31
[Convert the percent to decimal by dividing with 100.]

= 1 - 0.31 = 0.69
P (not red) = 1 - P(red)
[Probability of an event not happening = 1 - probability of the event happening.]

So, P(not red) is 69%.
[Convert the decimal to percent by multiplying with 100.]

6.
What is the probability of not getting the newspaper on time, if the probability of getting it on time is 42.4%?
 a. 56.1 b. 61.1 c. 59.1 d. 57.6

Solution:

P(on time) = 42.4% = 0.424

P(not on time) = 1 - 0.424 = 0.576
[Subtract]

There is 57.6% chance of not getting the newspaper on time.

7.
The letters C, O, M, P, E, T, I, T, I, O, N are written on cards and put in a hat. One card is selected at random. What is the probability that the card selected bears a consonant?
 a. $\frac{4}{11}$ b. $\frac{5}{11}$ c. $\frac{6}{11}$ d. $\frac{2}{11}$

Solution:

There are six cards on which consonants ('C', 'M', 'P', 'T', 'N') are written.

Number of favorable outcomes = Number of cards having consonants = 6

Number of possible outcomes = Total number of cards = 11

Probability of drawing a card having consonant = Number of favorable outcomes / number of possible outcomes = 6 / 11

8.
Olga has 8 dollars, 6 nickels, and 10 dimes in her purse. What is the probability of selecting a dime from her purse?
 a. $\frac{10}{11}$ b. $\frac{1}{24}$ c. $\frac{5}{12}$ d. $\frac{1}{14}$

Solution:

Number of favorable outcomes = Number of dimes = 10

Number of possible outcomes = Total number of coins = 24

= 512
P(dime) = number of dimes / total number of coins = 10 / 24

Probability of selecting a dime is 5 / 12.

9.
20 out of 70 plants had black colored flowers and 50 had violet colored flowers. Find the probability that a plant had violet colored flowers.
 a. $\frac{1}{7}$ b. $\frac{5}{7}$ c. $\frac{4}{5}$ d. None of the above

Solution:

Number of favorable outcomes = Number of plants with violet colored flowers = 50

Number of possible outcomes = Total number of plants = 70

= 57
P(violet) = number of plants with violet colored flowers / total number of plants = 50 / 70
[Simplify.]

The probability that the plant had violet colored flowers is 5 / 7.

10.
A bag contains 15 yellow marbles, 5 black marbles and 15 red marbles. What are the odds in favor of selecting a black marble?
 a. $\frac{1}{30}$ b. $\frac{1}{5}$ c. $\frac{1}{6}$ d. $\frac{2}{7}$

Solution:

Number of favorable outcomes = Number of black marbles = 5

Number of unfavorable outcomes = Number of marbles excluding black = 30

Odds in favor of an event = Number of favorable outcomesNumber of unfavorable outcomes = 5 / 30 = 1 / 6

Odds in favor of selecting a black marble is 1 / 6 .