Place four pebbles on the sand in the form of a square. Keep adding
as few pebbles as necessary to double the area. How many extra
pebbles are added each time?
Suppose we allow ourselves to use three numbers less than 10 and
multiply them together. How many different products can you find?
How do you know you've got them all?
Investigate the different shaped bracelets you could make from 18
different spherical beads. How do they compare if you use 24 beads?
When two of these moons line up with the planet it is called a
'lunar eclipse'. When three line up with the planet it is called a
'double eclipse', when four do it is a 'triple eclipse' and so on.
Once in a while all seven moons line up with the planet and this is
called a 'super-eclipse'.
Moon $A$ completes a cycle round the planet in one Vuvvian year,
moon $B$ takes two years, moon $C$ takes three years, moon $D$
takes four years and so on.
How long is it between each 'super-eclipse' on the planet of