Many numbers can be expressed as the difference of two perfect squares. What do you notice about the numbers you CANNOT make?
There are lots of different methods to find out what the shapes are worth - how many can you find?
This article explains how to make your own magic square to mark a special occasion with the special date of your choice on the top line.
If $a\times b=2$, $b\times c=24$, $c\times a=3$ and $a$, $b$ and $c$ are all positive, what is the value of $a+b+c$?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
This problem is taken from the UKMT Mathematical Challenges.