Infinite series

  • Diminishing Returns
    problem

    Diminishing returns

    Age
    11 to 14
    Challenge level
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    How much of the square is coloured blue? How will the pattern continue?
  • Harmonically
    problem

    Harmonically

    Age
    16 to 18
    Challenge level
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    Is it true that a large integer m can be taken such that: 1 + 1/2 + 1/3 + ... +1/m > 100 ?
  • Generally Geometric
    problem

    Generally geometric

    Age
    16 to 18
    Challenge level
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    Generalise the sum of a GP by using derivatives to make the coefficients into powers of the natural numbers.
  • Circles ad infinitum
    problem

    Circles ad infinitum

    Age
    16 to 18
    Challenge level
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    A circle is inscribed in an equilateral triangle. Smaller circles touch it and the sides of the triangle, the process continuing indefinitely. What is the sum of the areas of all the circles?