There are several answers
The first one I couldn't resist - it depends on how fat the people are
trying to stand in the yard
The second one is 9
The third is that as this is a graphics forum, draw a square (remember to
hold the shift key to force a square). Duplicate it twice and move them all
so that you have 3 squares in a row with the right side of the first becoming
the left edge of the 2nd and the right edge of the 2nd the left edge of the
3rd. Group them and duplicate twice and move them so that they are on top of
each other. You now have a square yard with 9 square feet in it
