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Primes, averages, probability and data — medium level math challenge!
1. What is the next number in the Fibonacci sequence: 1, 1, 2, 3, 5, 8, 13, ?
💡 Each number is the sum of the two before it. 8 + 13 = 21.
2. What is the mean of 4, 8, 12, 16, 20?
💡 Mean = (4+8+12+16+20) ÷ 5 = 60 ÷ 5 = 12.
3. What is the LCM of 6, 8, and 12?
💡 LCM of 6, 8, 12 = 24. It is the smallest number divisible by all three.
4. A bag has 3 red, 4 blue, 5 green balls. What is the probability of picking a blue ball?
💡 P(blue) = 4/12 = 1/3. Total balls = 3+4+5 = 12.
5. If you flip a coin twice, what is the probability of getting two heads?
💡 P(H) × P(H) = 1/2 × 1/2 = 1/4.
6. Which of the following is NOT a prime number?
💡 21 = 3 × 7, so it is not prime. It has factors other than 1 and itself.
7. How many prime numbers are between 1 and 20?
💡 Prime numbers between 1 and 20: 2,3,5,7,11,13,17,19 — that is 8 primes.
8. What is the median of 3, 7, 9, 11, 15?
💡 The median is the middle value when sorted. Sorted: 3,7,9,11,15 — middle value is 9.
9. What is the mode of: 3, 5, 3, 7, 9, 3, 5?
💡 The mode is the most frequently occurring value. 3 appears 3 times, more than any other number.
10. What is the HCF (Highest Common Factor) of 24 and 36?
💡 Factors of 24: 1,2,3,4,6,8,12,24. Factors of 36: 1,2,3,4,6,9,12,18,36. HCF = 12.
11. What is the range of: 15, 22, 8, 31, 19?
💡 Range = Maximum - Minimum = 31 - 8 = 23.
12. What is the probability of rolling a 4 on a standard die?
💡 A standard die has 6 faces. Probability of rolling a 4 = 1/6.
13. What is 6! (6 factorial)?
💡 6! = 6 × 5 × 4 × 3 × 2 × 1 = 720.
14. In a class of 30 students, 18 are girls. What percentage are boys?
💡 Boys = 30 - 18 = 12. Percentage = (12/30) × 100 = 40%.
15. What is the sum of the first 10 natural numbers?
💡 Sum = n(n+1)/2 = 10×11/2 = 55. Or simply 1+2+3+4+5+6+7+8+9+10 = 55.