Mathematics

Probability

303 Questions

Probability measures the likelihood of an event occurring, such as rolling a specific number on a die or drawing a colored ball. Questions cover simple events, mutually exclusive outcomes, and dice or coin combinations. This topic is consistently asked in mathematics and reasoning sections of competitive exams.

dice probabilitycoin toss eventsdrawing balls probabilitiesplaying card problemsmutually exclusive events

Probability Questions

Multiple choice

What is the probability of rolling a 6 on a standard six-sided die, given that the die has already landed on an even number?

  1. 1/3

  2. 1/2

  3. 1/4

  4. 1/6

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There are 3 even numbers on a standard six-sided die (2, 4, and 6), and only one of them is a 6. Therefore, the probability of rolling a 6, given that the die has already landed on an even number, is 1/3.

Multiple choice

What is the probability of rolling a 6 on a standard six-sided die, given that the die has already landed on a number greater than 3?

  1. 1/2

  2. 1/3

  3. 1/4

  4. 1/6

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There are 3 numbers greater than 3 on a standard six-sided die (4, 5, and 6), and 2 of them are even (4 and 6). Therefore, the probability of rolling a 6, given that the die has already landed on a number greater than 3, is 2/3.

Multiple choice

What is the probability of rolling a 6 on a standard six-sided die, given that the die has already landed on a number that is not a multiple of 3?

  1. 1/2

  2. 1/3

  3. 1/4

  4. 1/6

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There are 4 numbers that are not multiples of 3 on a standard six-sided die (1, 2, 4, and 5), and 2 of them are even (2 and 4). Therefore, the probability of rolling a 6, given that the die has already landed on a number that is not a multiple of 3, is 2/4, which simplifies to 1/2.

Multiple choice

What is the probability of rolling a 6 on a standard six-sided die, given that the die has already landed on a number that is not a multiple of 2?

  1. 1/3

  2. 1/2

  3. 1/4

  4. 1/6

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There are 5 numbers that are not multiples of 2 on a standard six-sided die (1, 3, 4, 5, and 6), and 2 of them are even (4 and 6). Therefore, the probability of rolling a 6, given that the die has already landed on a number that is not a multiple of 2, is 2/5.

Multiple choice

What is the probability of rolling a 6 on a standard six-sided die, given that the die has already landed on a number that is not a multiple of 4?

  1. 1/2

  2. 1/3

  3. 1/4

  4. 1/6

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There are 4 numbers that are not multiples of 4 on a standard six-sided die (1, 2, 3, and 5), and 2 of them are even (2 and 4). Therefore, the probability of rolling a 6, given that the die has already landed on a number that is not a multiple of 4, is 2/4, which simplifies to 1/2.

Multiple choice

What is the probability of rolling a 6 on a standard six-sided die, given that the die has already landed on a number that is not a multiple of 5?

  1. 1/2

  2. 1/3

  3. 1/4

  4. 1/6

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There are 5 numbers that are not multiples of 5 on a standard six-sided die (1, 2, 3, 4, and 6), and 2 of them are even (2 and 4). Therefore, the probability of rolling a 6, given that the die has already landed on a number that is not a multiple of 5, is 2/5.

Multiple choice

What is the probability of rolling a 6 on a standard six-sided die, given that the die has already landed on a number that is not a multiple of 6?

  1. 1/2

  2. 1/3

  3. 1/4

  4. 1/6

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There are 5 numbers that are not multiples of 6 on a standard six-sided die (1, 2, 3, 4, and 5), and 2 of them are even (2 and 4). Therefore, the probability of rolling a 6, given that the die has already landed on a number that is not a multiple of 6, is 2/5.

Multiple choice

A bag contains 6 red balls, 4 blue balls, and 2 green balls. If we randomly select 3 balls from the bag, what is the probability of getting exactly 2 red balls and 1 blue ball?

  1. 1/10

  2. 1/15

  3. 1/20

  4. 1/25

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

There are a total of 6 + 4 + 2 = 12 balls in the bag. The number of ways to choose 2 red balls out of 6 is C(6, 2) = 15. The number of ways to choose 1 blue ball out of 4 is C(4, 1) = 4. Therefore, the total number of ways to choose 2 red balls and 1 blue ball is 15 x 4 = 60. The probability of getting exactly 2 red balls and 1 blue ball is 60 / 12^3 = 1/15.

Multiple choice

A bag contains 10 red balls, 8 blue balls, and 6 green balls. If we randomly select 4 balls from the bag, what is the probability of getting at least 1 red ball?

  1. 1/2

  2. 2/5

  3. 3/5

  4. 4/5

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The probability of getting at least 1 red ball is equal to 1 minus the probability of getting no red balls. The probability of getting no red balls is given by (8/24)^4 = 1/256. Therefore, the probability of getting at least 1 red ball is 1 - 1/256 = 4/5.

Multiple choice

A bag contains 10 red balls, 8 blue balls, and 6 green balls. If we randomly select 4 balls from the bag, what is the probability of getting exactly 2 red balls, 1 blue ball, and 1 green ball?

  1. 1/10

  2. 1/15

  3. 1/20

  4. 1/25

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

There are a total of 10 + 8 + 6 = 24 balls in the bag. The number of ways to choose 2 red balls out of 10 is C(10, 2) = 45. The number of ways to choose 1 blue ball out of 8 is C(8, 1) = 8. The number of ways to choose 1 green ball out of 6 is C(6, 1) = 6. Therefore, the total number of ways to choose 2 red balls, 1 blue ball, and 1 green ball is 45 x 8 x 6 = 2160. The probability of getting exactly 2 red balls, 1 blue ball, and 1 green ball is 2160 / 24^4 = 1/20.

Multiple choice

A bag contains 6 red balls, 4 blue balls, and 2 green balls. If you randomly select 3 balls from the bag without replacement, what is the probability of getting exactly 2 red balls and 1 blue ball?

  1. 1/5

  2. 1/10

  3. 1/15

  4. 1/20

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

To solve this probability problem, we can use conditional probability. First, we calculate the probability of selecting 2 red balls from the 6 red balls: P(2 red) = C(6, 2) / C(12, 2) = 15 / 66. Then, given that we have selected 2 red balls, we calculate the probability of selecting 1 blue ball from the remaining 10 balls: P(1 blue | 2 red) = C(4, 1) / C(10, 1) = 4 / 10. Multiplying these probabilities, we get P(2 red and 1 blue) = P(2 red) * P(1 blue | 2 red) = (15 / 66) * (4 / 10) = 1/10.

Multiple choice

A coin is tossed 10 times. What is the probability of getting exactly 5 heads?

  1. 1/1024

  2. 1/256

  3. 1/512

  4. 1/128

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is a classic probability problem involving binomial distribution. The formula for binomial distribution is P(x) = (n! / (x!(n-x)!)) * p^x * q^(n-x), where n is the number of trials, x is the number of successes, p is the probability of success, and q is the probability of failure. In this case, n = 10, x = 5, p = 1/2, and q = 1/2. Plugging these values into the formula, we get P(5) = (10! / (5!(10-5)!)) * (1/2)^5 * (1/2)^(10-5) = 252 / 1024 = 1/4.

Multiple choice

A coin is tossed 10 times. What is the probability of getting exactly 5 heads?

  1. 0.246

  2. 0.256

  3. 0.266

  4. 0.276

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The probability of getting exactly 5 heads in 10 tosses is (P(X = 5) = \binom{10}{5} (0.5)^5 (0.5)^5 = 0.246).

Multiple choice

A die is rolled 6 times. What is the probability of getting exactly 3 sixes?

  1. 0.133

  2. 0.143

  3. 0.153

  4. 0.163

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The probability of getting exactly 3 sixes in 6 rolls is (P(X = 3) = \binom{6}{3} (1/6)^3 (5/6)^3 = 0.143).

Multiple choice

A bag contains 6 red balls, 4 blue balls, and 2 green balls. How many ways can you select 3 balls from the bag if you must select at least one ball of each color?

  1. 120

  2. 144

  3. 168

  4. 192

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is a combination problem with restrictions. First, you need to select 1 red ball from 6 red balls, which can be done in 6 ways. Then, you need to select 1 blue ball from 4 blue balls, which can be done in 4 ways. Finally, you need to select 1 green ball from 2 green balls, which can be done in 2 ways. So, the total number of ways is 6 * 4 * 2 = 144.