Explaining, convincing and proving
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problemHow many tours visit each vertex of a cube once and only once? How many return to the starting point? - 
problemThe spider and the fly
A spider is sitting in the middle of one of the smallest walls in a room and a fly is resting beside the window. What is the shortest distance the spider would have to crawl to catch the fly?
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problemFar horizon
An observer is on top of a lighthouse. How far from the foot of the lighthouse is the horizon that the observer can see?
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problemThe tall tower
As you come down the ladders of the Tall Tower you collect useful spells. Which way should you go to collect the most spells?
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problemWater pistols
With n people anywhere in a field each shoots a water pistol at the nearest person. In general who gets wet? What difference does it make if n is odd or even? - 
problemThe bridges of Konigsberg
Investigate how networks can be used to solve a problem for the 18th Century inhabitants of Konigsberg.
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problemTourism
If you can copy a network without lifting your pen off the paper and without drawing any line twice, then it is traversable. Decide which of these diagrams are traversable.
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problemPainted cube
Imagine a large cube made from small red cubes being dropped into a pot of yellow paint. How many of the small cubes will have yellow paint on their faces?
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problemTilted squares
It's easy to work out the areas of most squares that we meet, but what if they were tilted?