Canada Grade 8 Math Probability concepts and experiments

A bag contains 3 red marbles, 5 blue marbles, and 2 green marbles. What is the probability of drawing a blue marble from the bag?

Answer explanation

The total number of marbles is 3 red + 5 blue + 2 green = 10. The probability of drawing a blue marble is the number of blue marbles (5) divided by the total number of marbles (10), which simplifies to \frac{1}{2}.

If you roll a fair six-sided die, what is the probability of rolling a number greater than 4?

Answer explanation

To find the probability of rolling a number greater than 4 on a six-sided die, we consider the outcomes: 5 and 6. There are 2 favorable outcomes out of 6 total outcomes, giving a probability of \( \frac{2}{6} = \frac{1}{3} \).

A coin is flipped twice. What is the probability of getting two heads?

Answer explanation

When flipping a coin twice, there are 4 possible outcomes: HH, HT, TH, TT. Only one outcome (HH) results in two heads. Thus, the probability is \frac{1}{4}.

A spinner is divided into 4 equal sections numbered 1 to 4. What is the probability of the spinner landing on an even number?

Answer explanation

The even numbers on the spinner are 2 and 4. There are 2 favorable outcomes (2, 4) out of 4 total sections. Thus, the probability of landing on an even number is \( \frac{2}{4} = \frac{1}{2} \).

In a class of 30 students, 18 are girls. If a student is chosen at random, what is the probability that the student is a boy?

Answer explanation

In a class of 30 students, with 18 girls, there are 12 boys (30 - 18 = 12). The probability of selecting a boy is the number of boys divided by the total number of students: 12/30 = 2/5. However, the correct answer is 1/3, indicating a miscalculation.

A deck of cards has 52 cards. What is the probability of drawing a queen from the deck?

Answer explanation

A standard deck has 52 cards, including 4 queens. The probability of drawing a queen is the number of queens divided by the total number of cards: \( \frac{4}{52} = \frac{1}{13} \). Thus, the correct answer is \( \frac{1}{13} \).

If you roll two six-sided dice, what is the probability of the sum being 7?

Answer explanation

To find the probability of rolling a sum of 7 with two dice, count the successful outcomes: (1,6), (2,5), (3,4), (4,3), (5,2), (6,1) — a total of 6 outcomes. There are 36 possible outcomes when rolling two dice, so the probability is \frac{6}{36} = \frac{1}{6}.

A jar contains 4 red, 3 blue, and 3 yellow candies. What is the probability of picking a yellow candy?

Answer explanation

The total number of candies is 4 red + 3 blue + 3 yellow = 10. The probability of picking a yellow candy is the number of yellow candies (3) divided by the total number of candies (10), which is \frac{3}{10}.

What is the probability of drawing an ace from a standard deck of 52 cards?

Answer explanation

A standard deck has 52 cards, including 4 aces. The probability of drawing an ace is the number of favorable outcomes (4) divided by the total outcomes (52), which simplifies to \( \frac{1}{13} \).

A number is chosen at random from 1 to 10. What is the probability that the number is a prime number?

Answer explanation

The prime numbers between 1 and 10 are 2, 3, 5, and 7, totaling 4 prime numbers. Since there are 10 possible numbers, the probability is \( \frac{4}{10} = \frac{2}{5} \), which is the correct answer.