# Probability Quiz

**QUESTIONS**

1. The probability of event A occurring is equal to...

A) Number of possible outcomes / number of total outcomes

B) Number of total outcomes / number of possible outcomes

2. All probabilities fall between...

A) 0 - 1

B) -1 - 1

3. The word "and" in probability should trigger the use of...

A) Addition

B) Multiplication

4. The word "or" in probability should trigger the use of...

A) Addition

B) Multiplication

5. Probabilities are usually shown as...

A) Whole numbers

B) Decimals or percentages

6. The combined probabilities of the ending points on a decision tree will equal...

A) 1

B) 10

**ANSWER KEY:**

**1A, 2A, 3B, 4A, 5B, 6A**

**PRACTICE PROBLEMS**

1. If you were to pick a card from a deck at random, what is the probability of selecting a diamond?

2. If you were to pick a card from a deck at random, what is the probability of selecting the two of diamonds?

3. You decide to pull three cards from a deck at random. The first card is the two of hearts; the second card is the ace of spades. On the the third draw, what is the probability of selecting an ace? What is the probability of selecting a spade?

4. If you were to flip a coin, what is the probability of landing on heads?

5. If you were to flip a coin, what is the probability of landing on heads twice in a row?

6. If you were to roll a single die, what is the probability of rolling an even number?

7. If you were to roll a single die, what is the probability of rolling a prime number?

8. If you were to roll a pair of dice, what is the probability that the sum of the two numbers will be even?

**ANSWER KEY:**

**1: 13/52, which simplifies to 1/4**

**2: 1/52**

**3: 3/50; 12/50, which simplifies to 6/25**

**4: 50%**

**5: Essentially asking: "What is the probability of landing on heads AND then landing on heads again?"**

**AND -> MULTIPLICATION**

**.50 x .50 = .25**

**6:**

**Number of possible outcomes = 3 (2,4,6)**

**Total outcomes = 6 (1,2,3,4,5,6)**

**3/6 = .50**

**7:**

**Number of possible outcomes = 3 (2,3,5)**

**Number of total outcomes = 6 (1,2,3,4,5,6)**

**3/6 = .50**

**8:**

**Number of possible outcomes = 18**

**Number of total outcomes = 36**

**18/36 = .50**