ou don;t have to take my word for it, this is the explanaition as given by a doctor of mathematics...
"If this is a mile:
+---+
then this is a "one mile square," a square one mile on each side whose
area is called one square mile:
+---+
| |
+---+
and this is ten square miles:
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
But "ten miles square" (or "ten miles squared") means we make a square
ten miles on a side:
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
| | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+
If you count, or think a bit, you'll see that 10 miles square is
actually 100 square miles, ten times as much as 10 square miles."
It all depends on whether you say miles square(d) or square miles.