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?
This problem is featured in
Maths Trails - Excel in Problem Solving, one of the books in the
Maths Trails series written by members of the NRICH Team and
published by Cambridge University Press. For more details about the
other books in the series, please see our publications page .