Chapter 5 Probability - Review

On a true-false question, there is a 50% chance of getting the answer correct.

• rolling an even number on a fair number cube

• rolling a 1 or a 2 on a fair number cube

• spinning a 1 on a spinner with 4 equal

  sections labeled 1-4

• spinning a 1 or a 2 on a spinner with 10 equal sections labeled 1-10

Answer explanation

Rolling an even number on a fair number cube has a probability of 3 out of 6 (2, 4, 6), which is 50%. This matches the 50% chance of getting a true-false question correct.

The weather report shows that there is a 33 1/3% chance of rain.

• rolling an even number on a fair number cube

• rolling a 1 or a 2 on a fair number cube

• spinning a 1 on a spinner with 4 equal

  sections labeled 1-4

• spinning a 1 or a 2 on a spinner with 10 equal sections labeled 1-10

Answer explanation

The chance of rain is 33 1/3%, which is equivalent to 1/3. Rolling a 1 or a 2 on a fair number cube (which has 6 sides) gives a probability of 2/6 or 1/3, matching the rain probability.

Twenty-five percent of the time you are late to school.

• rolling an even number on a fair number cube

• rolling a 1 or a 2 on a fair number cube

• spinning a 1 on a spinner with 4 equal

  sections labeled 1-4

• spinning a 1 or a 2 on a spinner with 10 equal sections labeled 1-10

Answer explanation

Spinning a 1 on a spinner with 4 sections gives a probability of 1/4 or 25%, matching the 25% chance of being late to school. Other options do not yield the same probability.

A doctor’s office cancels appointments 20% of the time.

• rolling an even number on a fair number cube

• rolling a 1 or a 2 on a fair number cube

• spinning a 1 on a spinner with 4 equal

  sections labeled 1-4

• spinning a 1 or a 2 on a spinner with 10 equal sections labeled 1-10

Answer explanation

The doctor’s office cancels appointments 20% of the time, which is equivalent to a probability of 0.2. Spinning a 1 or a 2 on a spinner with 10 sections gives a probability of 2/10 or 20%, matching the cancellation rate.

There are three different colored candies: red, green, and white. The probability of selecting a red candy is 2/5, and the probability of selecting a green candy is 1/4. What is the probability of selecting a white candy?

• 1/2

• 1/5

• 3/10

• 7/20

Answer explanation

The total probability must equal 1. Given P(red) = 2/5 and P(green) = 1/4, we find P(white) = 1 - (2/5 + 1/4) = 1 - (8/20 + 5/20) = 1 - 13/20 = 7/20. Thus, the probability of selecting a white candy is 7/20.

The letters in the word APRIL are put into a bag and drawn randomly.

• a. P(A) = 1/5,

  b. P(vowel’) = 3/5,

  c. P(consonant) = 2/5

• a. P(A) = 1/4,

  b. P(vowel’) = 2/5,

  c. P(consonant) = 1/5

• a. P(A) = 1/5,

  b. P(vowel’) = 2/5,

  c. P(consonant) = 3/5

• a. P(A) = 1/6,

  b. P(vowel’) = 1/5,

  c. P(consonant) = 2/5

Answer explanation

In the word APRIL, there are 5 letters: 2 vowels (A, I) and 3 consonants (P, R, L). Thus, P(vowel) = 2/5 and P(consonant) = 3/5. The correct probabilities are: P(A) = 1/5, P(vowel) = 3/5, P(consonant) = 2/5.

In Mr. Martinez’s sixth period class, there are 8 bus riders and 12 walkers. What is the probability of randomly selecting a student that walks to school?

• 2/5

• 3/5

• 2/3

• 4/5

Answer explanation

To find the probability of selecting a walker, divide the number of walkers (12) by the total number of students (8 bus riders + 12 walkers = 20). Thus, the probability is 12/20, which simplifies to 3/5.

The weather report says there is a 30% chance of rain. What is the probability that it does not rain?

• 30%

• 50%

• 70%

• 100%

Answer explanation

The weather report indicates a 30% chance of rain, meaning there is a 70% chance it does not rain. Therefore, the correct answer is 70%.

The numbers 1 - 12 are written on a card and placed in a bag. What is the probability that a number divisible by 3 is drawn? What represents its complement?

• 1/4, 3/4

• 1/3, 2/3

• 1/2, 1/2

• 1/6, 5/6

Answer explanation

There are 4 numbers (3, 6, 9, 12) divisible by 3 out of 12 total numbers. Thus, the probability is 4/12 = 1/3. The complement, numbers not divisible by 3, is 8/12 = 2/3. Hence, the correct choice is 1/3, 2/3.

In the movie drawer, there are seven action movies, five comedies, and three dramas. What is the probability of choosing an action or a comedy?

• 4/5

• 1/3

• 2/5

• 3/5

Answer explanation

To find the probability of choosing an action or a comedy, add the number of action movies (7) and comedies (5) to get 12. The total number of movies is 15. Thus, the probability is 12/15, which simplifies to 4/5.