When is $7^n + 3^n$ a multiple of 10? Can you prove the result by two different methods?
Which is the bigger, 9^10 or 10^9 ? Which is the bigger, 99^100 or 100^99 ?
Take a look at the video showing rhombuses and their diagonals...
In a city with a grid system of roads, how do you get from A to B?
What's special about the area of quadrilaterals drawn in a square?
Can you minimise the amount of wood needed to build the roof of my garden shed?