Stage: 3 and 4 Challenge Level:
Ask yourself "is there anything special about the angle between the
diagonals of a rhombus?'' Now think again about the path of X as
the linkage moves.
This problem was at first a "tough nut'' to crack! A
friend of mine calls these sort of questions, where no-one can find
a solution for quite a long while, 'Mars Bar question'. Perhaps
your teacher or your Mum will buy you a Mars Bar if you can solve