Three squares
On three identical square cards I wrote 3 × 3 magic squares (where the sums of each row, column and major diagonal are equal) using the numbers 1 to 9 on the first, 10 to 18 on the second and 19 to 27 on the third. I formed them into a sandwich in some order. I then found that I could push a pin through the cards so that it passed through three multiples of three. Furthermore, writing the three numbers in order along the pin gave a five-figure perfect square. One number on the middle card was…
