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?
In the $2 \times 2$ multiplication square below, the boxes at
the end of each row and the foot of each column give the result of
multiplying the two numbers in that row or column.
The $3 \times3$ multiplication square below works in
the same way. The boxes at the end of each row and the foot of each
column give the result of multiplying the three numbers in that row
The numbers $1 - 9$ may be used once and once only.
Can you work out the arrangement of the digits in the square so
that the given products are correct?