Year 9 Explaining, convincing and proving

  • A cardboard carton of cherries.
    problem
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    Fruity Totals

    Age
    7 to 16
    Challenge level
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    In this interactivity each fruit has a hidden value. Can you deduce what each one is worth?

  • Xavi's T-shirt
    problem
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    Xavi's T-Shirt

    Age
    7 to 16
    Challenge level
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    How much can you read into a T-shirt?

  • Blue and White
    problem
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    Blue and White

    Age
    11 to 14
    Challenge level
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    Identical squares of side one unit contain some circles shaded blue. In which of the four examples is the shaded area greatest?

  • Special Numbers
    problem
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    Special Numbers

    Age
    11 to 14
    Challenge level
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    My two digit number is special because adding the sum of its digits to the product of its digits gives me my original number. What could my number be?

  • Tilted Squares
    problem
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    Tilted Squares

    Age
    11 to 14
    Challenge level
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    It's easy to work out the areas of most squares that we meet, but what if they were tilted?

  • Do you feel lucky?
    problem
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    Do You Feel Lucky?

    Age
    11 to 14
    Challenge level
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    Some people offer advice on how to win at games of chance, or how to influence probability in your favour. Can you decide whether advice is good or not?

  • What does random look like?
    problem
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    What Does Random Look Like?

    Age
    11 to 14
    Challenge level
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    Engage in a little mathematical detective work to see if you can spot the fakes.

  • Legs Eleven
    problem
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    Legs Eleven

    Age
    11 to 14
    Challenge level
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    Take any four digit number. Move the first digit to the end and move the rest along. Now add your two numbers. Did you get a multiple of 11?

  • Think of Two Numbers
    problem
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    Think of Two Numbers

    Age
    11 to 14
    Challenge level
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    Think of two whole numbers under 10, and follow the steps. I can work out both your numbers very quickly. How?

  • An Unusual Shape
    problem
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    An Unusual Shape

    Age
    11 to 14
    Challenge level
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    Can you maximise the area available to a grazing goat?

  • Subtended angles
    problem
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    Subtended Angles

    Age
    11 to 14
    Challenge level
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    What is the relationship between the angle at the centre and the angles at the circumference, for angles which stand on the same arc? Can you prove it?

  • Triangle Numbers
    problem
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    Triangle Numbers

    Age
    11 to 14
    Challenge level
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    Take a look at the multiplication square. The first eleven triangle numbers have been identified. Can you see a pattern? Does the pattern continue?

  • The Tower of Hanoi - three wooden poles, with several coloured rings of decreasing sizes on the middle pole.
    problem
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    Tower of Hanoi

    Age
    11 to 14
    Challenge level
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    The Tower of Hanoi is an ancient mathematical challenge. Working on the building blocks may help you to explain the patterns you notice.

  • Fill Me Up
    problem
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    Fill Me Up

    Age
    11 to 14
    Challenge level
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    Can you sketch graphs to show how the height of water changes in different containers as they are filled?

  • What numbers can we make now?
    problem
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    What Numbers Can We Make Now?

    Age
    11 to 14
    Challenge level
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    Imagine we have four bags containing numbers from a sequence. What numbers can we make now?

  • Quadrilaterals in a Square
    problem
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    Quadrilaterals in a Square

    Age
    11 to 14
    Challenge level
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    What's special about the area of quadrilaterals drawn in a square?

  • Impossibilities
    problem
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    Impossibilities

    Age
    11 to 14
    Challenge level
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    Just because a problem is impossible doesn't mean it's difficult...

  • Overlaps
    problem
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    Overlaps

    Age
    11 to 14
    Challenge level
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    Can you find ways to put numbers in the overlaps so the rings have equal totals?

  • Reversals
    problem
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    Reversals

    Age
    11 to 14
    Challenge level
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    Where should you start, if you want to finish back where you started?

  • Garden Shed
    problem
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    Garden Shed

    Age
    11 to 14
    Challenge level
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    Can you minimise the amount of wood needed to build the roof of my garden shed?

  • Star Polygons
    problem
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    Star Polygons

    Age
    11 to 14
    Challenge level
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    Draw some stars and measure the angles at their points. Can you find and prove a result about their sum?

  • The Farmers' Field Boundary
    problem
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    The Farmers' Field Boundary

    Age
    11 to 14
    Challenge level
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    The farmers want to redraw their field boundary but keep the area the same. Can you advise them?

  • Cuboids
    problem
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    Cuboids

    Age
    11 to 14
    Challenge level
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    Can you find a cuboid that has a surface area of exactly 100 square units. Is there more than one? Can you find them all?

  • Which solids can we make?
    problem
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    Which Solids Can We Make?

    Age
    11 to 14
    Challenge level
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    Interior angles can help us to work out which polygons will tessellate. Can we use similar ideas to predict which polygons combine to create semi-regular solids?

  • Semi-regular Tessellations
    problem
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    Semi-Regular Tessellations

    Age
    11 to 16
    Challenge level
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    Semi-regular tessellations combine two or more different regular polygons to fill the plane. Can you find all the semi-regular tessellations?

  • problem
    Favourite

    Cyclic Quadrilaterals

    Age
    11 to 16
    Challenge level
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    Draw some quadrilaterals on a 9-point circle and work out the angles. Is there a theorem?

  • problem
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    Marbles in a Box

    Age
    11 to 16
    Challenge level
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    How many winning lines can you make in a three-dimensional version of noughts and crosses?

  • Product Sudoku
    problem
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    Product Sudoku

    Age
    11 to 16
    Challenge level
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    The clues for this Sudoku are the product of the numbers in adjacent squares.

  • Pythagoras Proofs
    problem
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    Pythagoras Proofs

    Age
    11 to 16
    Challenge level
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    Can you make sense of these three proofs of Pythagoras' Theorem?

  • Triangle in a Trapezium
    problem
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    Triangle in a Trapezium

    Age
    11 to 16
    Challenge level
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    Can you find and prove the relationship between the area of a trapezium and the area of a triangle constructed within it?