Explaining, convincing and proving

  • Common Divisor
    problem

    Common Divisor

    Age
    14 to 18
    Challenge level
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    Can you find out what numbers divide these expressions? Can you prove that they are always divisors?

  • Network Trees
    problem

    Network Trees

    Age
    14 to 18
    Challenge level
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    Explore some of the different types of network, and prove a result about network trees.

  • A powerful Matrix
    problem

    A Powerful Matrix

    Age
    14 to 18
    Challenge level
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    What happens when you find the powers of this matrix?

  • Proof Sorter - Quadratic Equation
    interactivity

    Proof Sorter - Quadratic Equation

    Age
    14 to 18
    Challenge level
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    This is an interactivity in which you have to sort the steps in the completion of the square into the correct order to prove the formula for the solutions of quadratic equations.

  • Sixational
    problem

    Sixational

    Age
    14 to 18
    Challenge level
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    The nth term of a sequence is given by the formula n^3 + 11n. Find the first four terms of the sequence given by this formula and the first term of the sequence which is bigger than one million. Prove that all terms of the sequence are divisible by 6.

  • Pent
    problem

    Pent

    Age
    14 to 18
    Challenge level
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    The diagram shows a regular pentagon with sides of unit length. Find all the angles in the diagram. Prove that the quadrilateral shown in red is a rhombus.

  • Calculating with cosines
    problem

    Calculating With Cosines

    Age
    14 to 18
    Challenge level
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    If I tell you two sides of a right-angled triangle, you can easily work out the third. But what if the angle between the two sides is not a right angle?

  • Impossible sums
    problem

    Impossible Sums

    Age
    14 to 18
    Challenge level
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    Which numbers cannot be written as the sum of two or more consecutive numbers?

  • Difference of odd squares
    problem

    Difference of Odd Squares

    Age
    14 to 18
    Challenge level
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    $40$ can be written as $7^2 - 3^2.$ Which other numbers can be written as the difference of squares of odd numbers?

  • The Converse of Pythagoras
    problem

    The Converse of Pythagoras

    Age
    14 to 18
    Challenge level
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    Can you prove that triangles are right-angled when $a^2+b^2=c^2$?