Six Hard Math Brain‑Teasers

A collection of six demanding riddles that blend arithmetic tricks with logical twists, crafted to stretch even seasoned problem solvers.

logic puzzlesbrain teasercritical thinkinghard puzzlenumber theorymath riddlesmental math
Difficulty:HARD

Quiz Details

Questions6
CategoryRiddles & Brain Teasers
DifficultyHARD
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Quiz Questions

Answer all questions below and test your knowledge.

  1. 1

    A number is three times the sum of its digits. What is the smallest positive integer that satisfies this condition?

    Question 1
  2. 2

    Start with 2 and 3; each subsequent term equals the product of the previous two terms minus the previous term. What is the fourth term?

    Question 2
  3. 3

    A rectangular garden has integer side lengths. Its area exceeds its perimeter by 30 square meters. What is the smallest possible perimeter?

    Question 3
  4. 4

    Find the least positive integer that leaves remainder 4 when divided by 7, remainder 6 when divided by 9, and remainder 8 when divided by 11.

    Question 4
  5. 5

    A right triangle has integer sides. The area equals 84 and the perimeter is minimal among all such triangles. What is the length of the hypotenuse?

    Question 5
  6. 6

    Consider the infinite series 1/2 + 1/4 + 1/8 + … . What is the smallest integer n such that the sum of the first n terms exceeds 0.99?

    Question 6

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