There are of course six different places between the seven figures in
which a cut may be made, and the secret lies in keeping one strip intact
and cutting each of the other six in a different place. After the cuts
have been made there are a large number of ways in which the thirteen
pieces may be placed together so as to form a magic square. Here is one
of them:--
[Illustration:
+-------------+
|1 2 3 4 5 6 7|
+---------+---+
|3 4 5 6 7|1 2|
+-----+---+---+
|5 6 7|1 2 3 4|
+-+---+-------+
|7|1 2 3 4 5 6|
+-+---------+-+
|2 3 4 5 6 7|1|
+-------+---+-+
|4 5 6 7|1 2 3|
+---+---+-----+
|6 7|1 2 3 4 5|
+---+---------+
]
The arrangement has some rather interesting features. It will be seen
that the uncut strip is at the top, but it will be found that if the
bottom row of figures be placed at the top the numbers will still form a
magic square, and that every successive removal from the bottom to the
top (carrying the uncut strip stage by stage to the bottom) will produce
the same result. If we imagine the numbers to be on seven complete
_perpendicular_ strips, it will be found that these columns could also
be moved in succession from left to right or from right to left, each
time producing a magic square.