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

A box contains 10 red balls, 12 blue balls, and 15 green balls. How many ways can you select 5 balls from the box if you must select at least 2 red balls?

  1. 2380

  2. 3003

  3. 4095

  4. 5005

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

This is a combination problem with restrictions. First, you need to select 2 red balls from 10 red balls, which can be done in C(10, 2) = 45 ways. Then, you need to select 3 balls from the remaining 27 balls (12 blue balls + 15 green balls), which can be done in C(27, 3) = 2925 ways. So, the total number of ways is 45 * 2925 = 3003.

Multiple choice

A bag contains 8 red balls, 6 blue balls, and 4 green balls. How many ways can you select 4 balls from the bag if you must select at least 1 ball of each color?

  1. 336

  2. 420

  3. 504

  4. 588

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 8 red balls, which can be done in 8 ways. Then, you need to select 1 blue ball from 6 blue balls, which can be done in 6 ways. Finally, you need to select 1 green ball from 4 green balls, which can be done in 4 ways. So, the total number of ways is 8 * 6 * 4 = 420.

Multiple choice

A bag contains 10 red balls, 12 blue balls, and 15 green balls. How many ways can you select 5 balls from the bag if you must select at least 1 red ball and at least 1 blue ball?

  1. 3960

  2. 4320

  3. 4680

  4. 5040

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 10 red balls, which can be done in 10 ways. Then, you need to select 1 blue ball from 12 blue balls, which can be done in 12 ways. Finally, you need to select 3 more balls from the remaining 27 balls (15 green balls + 10 red balls + 12 blue balls), which can be done in C(27, 3) = 2925 ways. So, the total number of ways is 10 * 12 * 2925 = 4320.

Multiple choice

A bag contains 12 red balls, 10 blue balls, and 8 green balls. How many ways can you select 5 balls from the bag if you must select at least 2 red balls and at least 2 blue balls?

  1. 2520

  2. 2880

  3. 3240

  4. 3600

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

This is a combination problem with restrictions. First, you need to select 2 red balls from 12 red balls, which can be done in C(12, 2) = 66 ways. Then, you need to select 2 blue balls from 10 blue balls, which can be done in C(10, 2) = 45 ways. Finally, you need to select 1 more ball from the remaining 20 balls (8 green balls + 12 red balls + 10 blue balls), which can be done in 20 ways. So, the total number of ways is 66 * 45 * 20 = 2880.

Multiple choice

What is the probability of getting a head when flipping a fair coin?

  1. 0.5

  2. 0.25

  3. 0.75

  4. 1

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

Since there are two possible outcomes (head or tail) and each outcome is equally likely, the probability of getting a head is 1/2 or 0.5.

Multiple choice

What is the probability of getting exactly 3 heads when flipping a fair coin 5 times?

  1. 0.3125

  2. 0.25

  3. 0.125

  4. 0.0625

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

The probability of getting exactly 3 heads when flipping a fair coin 5 times can be calculated using the binomial distribution. The formula for the binomial distribution is P(x) = (nCx) * 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 = 5, x = 3, p = 0.5, and q = 0.5. Plugging these values into the formula, we get P(3) = (5C3) * 0.5^3 * 0.5^(5-3) = 0.3125.

Multiple choice

What is the probability of getting at least 2 heads when flipping a fair coin 4 times?

  1. 0.875

  2. 0.75

  3. 0.625

  4. 0.5

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

The probability of getting at least 2 heads when flipping a fair coin 4 times can be calculated by subtracting the probability of getting 0 or 1 head from 1. The probability of getting 0 heads is (0.5)^4 = 0.0625, and the probability of getting 1 head is 4 * (0.5)^4 * (0.5)^3 = 0.25. Therefore, the probability of getting at least 2 heads is 1 - 0.0625 - 0.25 = 0.875.

Multiple choice

What is the probability of getting a head when flipping a coin?

  1. $0.25$
  2. $0.5$
  3. $0.75$
  4. $1$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When flipping a coin, there are two possible outcomes: head or tail. Since both outcomes are equally likely, the probability of getting a head is $1/2 = 0.5$.

Multiple choice

What is the probability of getting two heads when flipping two coins?

  1. $0.25$
  2. $0.5$
  3. $0.75$
  4. $1$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When flipping two coins, there are four possible outcomes: HH, HT, TH, TT. Since each outcome is equally likely, the probability of getting two heads is $1/4 = 0.25$.

Multiple choice

In a fair coin toss, what is the Martingale strategy?

  1. Double the bet after each loss

  2. Double the bet after each win

  3. Keep the bet the same after each outcome

  4. Randomly change the bet amount

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

The Martingale strategy in a fair coin toss involves doubling the bet after each loss in an attempt to recoup the losses and eventually make a profit.

Multiple choice

What is the probability of rolling a 6 on a standard six-sided die?

  1. 1/2

  2. 1/3

  3. 1/4

  4. 1/6

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

The probability of rolling a specific number on a die is calculated by dividing 1 by the total number of possible outcomes. In this case, there are six possible outcomes (1, 2, 3, 4, 5, 6), so the probability of rolling a 6 is 1/6.

Multiple choice

What is the probability of getting at least one head when flipping a coin twice?

  1. 1/2

  2. 1/4

  3. 3/4

  4. 1

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

There are four possible outcomes when flipping a coin twice: HH, HT, TH, TT. Only one of these outcomes (TT) does not have at least one head. Therefore, the probability of getting at least one head is 3/4.

Multiple choice

What is the probability of getting a sum of 7 when rolling two fair six-sided dice?

  1. 1/6

  2. 1/12

  3. 1/18

  4. 1/36

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

There are 36 possible outcomes when rolling two six-sided dice. The outcomes that sum to 7 are (1, 6), (2, 5), (3, 4), (4, 3), (5, 2), and (6, 1). Therefore, the probability of getting a sum of 7 is 6/36, which simplifies to 1/6.

Multiple choice

What is the probability of getting a sum of 10 or less when rolling two fair six-sided dice?

  1. 1/2

  2. 2/3

  3. 3/4

  4. 5/6

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

There are 36 possible outcomes when rolling two six-sided dice. The outcomes that sum to 10 or less are (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (3, 1), (3, 2), (3, 3), (3, 4), (4, 1), (4, 2), (4, 3), (5, 1), (5, 2), (6, 1). Therefore, the probability of getting a sum of 10 or less is 21/36, which simplifies to 5/6.

Multiple choice

What is the probability of getting a sum of 12 or more when rolling two fair six-sided dice?

  1. 1/6

  2. 1/3

  3. 1/2

  4. 2/3

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

There are 36 possible outcomes when rolling two six-sided dice. The outcomes that sum to 12 or more are (6, 6), (5, 6), (6, 5), (4, 6), (6, 4), (3, 6), (6, 3), (2, 6), (6, 2). Therefore, the probability of getting a sum of 12 or more is 9/36, which simplifies to 1/4.