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Free Mensa IQ Number Series Completion Practice Test Flashcards

35 cards from real MENSA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 20 Free Mensa IQ Number Series Completion Practice Test flashcards as text

  1. What is the next number? 3, 7, 13, 21, 31, ?

    Answer: B. 43

    Differences: 4, 6, 8, 10, 12 — increasing by 2 each time. Next difference = 12, so 31 + 12 = 43.

  2. Complete the series: 2, 3, 5, 8, 13, 21, ?

    Answer: C. 34

    This is the Fibonacci sequence — each number is the sum of the two preceding ones: 13+21=34.

  3. Find the missing number: 1, 8, 27, 64, 125, ?

    Answer: C. 216

    These are perfect cubes: 1³, 2³, 3³, 4³, 5³. The next is 6³ = 216.

  4. What comes next? 100, 91, 83, 76, 70, ?

    Answer: A. 65

    Differences: -9, -8, -7, -6, -5. The decreasing differences reduce by 1 each time. Next difference = -5, so 70 - 5 = 65.

  5. Find the next number: 5, 10, 20, 40, 80, ?

    Answer: C. 160

    Each number is doubled: 5×2=10, 10×2=20, 20×2=40, 40×2=80, 80×2=160. This is a geometric sequence with ratio 2.

  6. Complete the sequence: 1, 4, 10, 20, 35, ?

    Answer: B. 56

    Differences: 3, 6, 10, 15 — these are triangular numbers. Next difference = 21. So 35 + 21 = 56. These are tetrahedral numbers.

  7. What is the missing term? 2, 6, 18, 54, ?, 486

    Answer: C. 162

    Each term is multiplied by 3: 2×3=6, 6×3=18, 18×3=54, 54×3=162, 162×3=486. The missing term is 162.

  8. Find the next number: 1, 1, 2, 6, 24, ?

    Answer: C. 120

    These are factorials: 0!=1, 1!=1, 2!=2, 3!=6, 4!=24, 5!=120.

  9. What comes next? 3, 6, 11, 18, 27, ?

    Answer: B. 38

    Differences: 3, 5, 7, 9 — odd numbers increasing by 2. Next difference = 11. So 27 + 11 = 38.

  10. Complete the series: 256, 128, 64, 32, ?

    Answer: B. 16

    Each number is halved: 256÷2=128, 128÷2=64, 64÷2=32, 32÷2=16.

  11. Find the missing number: 7, 14, 28, ?, 112, 224

    Answer: C. 56

    Each number is doubled: 7×2=14, 14×2=28, 28×2=56, 56×2=112, 112×2=224. The missing number is 56.

  12. What is the next term? 2, 5, 10, 17, 26, ?

    Answer: B. 37

    Pattern: n² + 1. 1²+1=2, 2²+1=5, 3²+1=10, 4²+1=17, 5²+1=26, 6²+1=37.

  13. Complete: 1, 3, 7, 15, 31, ?

    Answer: D. 63

    Each number = previous×2 + 1: 1×2+1=3, 3×2+1=7, 7×2+1=15, 15×2+1=31, 31×2+1=63.

  14. Find the next number: 10, 9, 7, 4, 0, ?

    Answer: C. -5

    Differences: -1, -2, -3, -4, -5. Each difference decreases by 1. So 0 + (-5) = -5.

  15. What comes next? 1, 2, 4, 7, 11, 16, ?

    Answer: C. 22

    Differences: 1, 2, 3, 4, 5, 6. Each difference increases by 1. Next = 16 + 6 = 22.

  16. Complete the sequence: 81, 27, 9, 3, ?

    Answer: B. 1

    Each term is divided by 3: 81÷3=27, 27÷3=9, 9÷3=3, 3÷3=1.

  17. Find the missing number: 3, 9, 27, 81, ?

    Answer: C. 243

    Each term is multiplied by 3 (powers of 3): 3¹, 3², 3³, 3⁴, 3⁵=243.

  18. What is the next term? 1, 5, 14, 30, 55, ?

    Answer: C. 91

    These are square pyramidal numbers: sum of 1², 2², 3²... Differences: 4, 9, 16, 25, 36. Next = 55 + 36 = 91.

  19. Complete: 0, 1, 3, 6, 10, 15, ?

    Answer: C. 21

    Triangular numbers: differences are 1, 2, 3, 4, 5, 6. Next = 15 + 6 = 21.

  20. What comes next? 4, 9, 25, 49, 121, ?

    Answer: B. 169

    These are squares of prime numbers: 2²=4, 3²=9, 5²=25, 7²=49, 11²=121, 13²=169.