Probability Skills

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

Answer explanation

The probability of drawing a blue marble is 5 out of the total 10 marbles, which simplifies to 1/2 or 5/10.

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

Answer explanation

To find the probability of rolling a number greater than 4, we count the favorable outcomes (5 and 6) out of the total outcomes (1 to 6). Therefore, the probability is 2/6 or 1/3.

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

Answer explanation

The probability of getting heads both times when flipping a coin twice is 1/4 because there are 4 possible outcomes (HH, HT, TH, TT) and only 1 of them results in heads both times.

In a class of 20 students, 9 are boys and 11 are girls. If a student is chosen at random, what is the probability that the student is a girl?

Answer explanation

The probability of choosing a girl is 11 out of 20 students, so the correct answer is 11/20.

A drawer contains 4 black socks, 5 white socks, and 3 grey socks. If a sock is picked at random, what is the probability it is not white?

Answer explanation

To find the probability of not picking a white sock, we calculate 1 - (probability of picking a white sock) = 1 - (5/12) = 7/12.

A bag contains 2 yellow, 3 red, and 5 green balls. Two balls are drawn at random. What is the probability that both are green?

Answer explanation

The probability of drawing the first green ball is 5/10. After drawing one green ball, there are 4 green balls left out of 9 total balls. Therefore, the probability of drawing the second green ball is 4/9. Multiplying these probabilities gives 10/45.

A school has a 60% chance of staying open during a snowstorm. What is the probability that it will close?

Answer explanation

The correct probability that the school will close during a snowstorm is 0.4, which is the complement of the 60% chance of staying open (1 - 0.6 = 0.4).

A spinner has 8 equal sections numbered from 1 to 8. What is the probability of spinning a number less than 3?

Answer explanation

To spin a number less than 3, there are 2 favorable outcomes (1 and 2) out of 8 total outcomes. Therefore, the probability is 2/8 or 1/4.

A box contains 15 chocolate, 10 vanilla, and 5 strawberry ice creams. If one ice cream is chosen at random, what is the probability it is vanilla?

Answer explanation

The probability of choosing a vanilla ice cream is 10 out of the total 30 ice creams, so the correct probability is 10/30 or 1/3.

A fair coin is flipped three times. What is the probability of getting exactly two heads?

Answer explanation

To calculate the probability of getting exactly two heads in three coin flips, we use the combination formula: C(3,2) = 3. The total number of outcomes is 2^3 = 8. Therefore, the probability is 3/8.