Mathematics Hard

Probability, Statistics and Number Theory

The toughest math quiz questions online — 20 tough questions spanning probability, statistics and number theory.

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1. Is 1 considered a prime number?

  • A. Yes
  • B. No ✓
  • C. Sometimes
  • D. Depends on context

💡 By modern mathematical definition, 1 is not considered a prime number since it has only one positive divisor.

2. What does standard deviation measure?

  • A. Average
  • B. Spread of data ✓
  • C. Median
  • D. Mode

💡 Standard deviation measures how spread out data points are from the mean.

3. What is the sum of the interior angles of a polygon with n sides?

  • A. (n-2) x 180 ✓
  • B. n x 180
  • C. (n+2) x 180
  • D. n x 90

💡 The sum of interior angles of any polygon is given by the formula (n-2) x 180 degrees.

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

  • A. 1/13 ✓
  • B. 1/26
  • C. 1/52
  • D. 4/52

💡 There are 4 aces in a 52-card deck, giving a probability of 4/52, which simplifies to 1/13.

5. What is a composite number?

  • A. A prime number
  • B. A number with more than two factors ✓
  • C. A number divisible only by 1
  • D. A negative number

💡 A composite number has more than two positive divisors, unlike a prime number.

6. What is the number of permutations of 3 items from a set of 5 (5P3)?

  • A. 10
  • B. 20
  • C. 60 ✓
  • D. 120

💡 Using the permutation formula, 5P3 equals 5 x 4 x 3 = 60.

7. What is a perfect square?

  • A. A number that is the product of an integer with itself ✓
  • B. A prime number
  • C. An odd number
  • D. A number divisible by 4

💡 A perfect square, like 4, 9, or 16, results from multiplying a whole number by itself.

8. What is the probability of not rolling a 6 on a die?

  • A. 1/6
  • B. 5/6 ✓
  • C. 4/6
  • D. 1/2

💡 Since there are 5 outcomes other than rolling a 6, out of 6 total, the probability is 5/6.

9. What is a twin prime?

  • A. A pair of prime numbers that differ by 2 ✓
  • B. A prime number squared
  • C. Two consecutive integers
  • D. A prime number divided by 2

💡 Twin primes are pairs of prime numbers that differ by exactly 2, such as 11 and 13.

10. What is a prime number?

  • A. A number divisible only by 1 and itself ✓
  • B. An even number
  • C. A number divisible by 2
  • D. A negative number

💡 A prime number has exactly two distinct positive divisors: 1 and itself.

11. What is 6! (6 factorial)?

  • A. 120
  • B. 360
  • C. 720 ✓
  • D. 840

💡 6! means 6 x 5 x 4 x 3 x 2 x 1, which equals 720.

12. What is 0.1 as a fraction?

  • A. 1/10 ✓
  • B. 1/100
  • C. 1/5
  • D. 1/20

💡 0.1 equals 1/10 as a fraction.

13. What is the number of ways to arrange 4 different books on a shelf?

  • A. 12
  • B. 16
  • C. 24 ✓
  • D. 32

💡 This is 4 factorial (4!), which equals 4 x 3 x 2 x 1 = 24.

14. What is the probability of flipping a coin and getting heads?

  • A. 1/4
  • B. 1/3
  • C. 1/2 ✓
  • D. 1

💡 A fair coin has two equally likely outcomes, so the probability of heads is 1/2.

15. What is the number of combinations of choosing 2 items from a set of 5 (5C2)?

  • A. 5
  • B. 10 ✓
  • C. 15
  • D. 20

💡 Using the combination formula, 5C2 equals 10.

16. What is the probability of rolling a sum of 7 with two dice?

  • A. 1/6 ✓
  • B. 1/9
  • C. 1/12
  • D. 5/36

💡 There are 6 combinations that sum to 7 out of 36 total outcomes, giving a probability of 1/6.

17. What is Goldbach's Conjecture about?

  • A. Every even integer greater than 2 can be expressed as the sum of two primes ✓
  • B. Every prime number is odd
  • C. Every number has a unique factorization
  • D. There are infinitely many primes

💡 Goldbach's Conjecture, still unproven, states that every even integer greater than 2 can be written as the sum of two prime numbers.

18. What is the probability of drawing a red card from a standard 52-card deck?

  • A. 1/4
  • B. 1/2 ✓
  • C. 1/3
  • D. 1/13

💡 Half of a standard deck's 52 cards are red, giving a probability of 1/2.

19. What is the probability of getting at least one head in two coin flips?

  • A. 1/4
  • B. 1/2
  • C. 3/4 ✓
  • D. 1

💡 Out of four equally likely outcomes (HH, HT, TH, TT), three include at least one head, giving 3/4.

20. In statistics, what does 'variance' measure?

  • A. The average
  • B. The middle value
  • C. The spread of data points ✓
  • D. The most frequent value

💡 Variance quantifies how much the data points in a set differ from the mean.

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