What happens to the perimeter of triangle ABC as the two smaller
circles change size and roll around inside the bigger circle?
Draw a 'doodle' - a closed intersecting curve drawn without taking pencil from paper. What can you prove about the intersections?
I want some cubes painted with three blue faces and three red faces. How many different cubes can be painted like that?
Four identical right angled triangles are drawn on the sides of
a square. Two face out, two face in. Congratulations Soh Yong Sheng
of Raffles Institution, Singapore and James of Hethersett High
School for your solution. The image
can be further expanded into a diagram containing 3 squares of
which two are the same size.
The two smallest quadrilaterals produced are squares as their
sides are all of the same length equal to the shortest side of the
triangle. The dots will form one line containing the diagonals of
the three squares as the sides of the squares are all perpendicular
or parallel to each other.
Here is another way of looking at it.