$mn$ People standing in a rectangular array
115833
$m \times n$ persons stand in $m$ rows and $n$ columns
123939
N circles in the plane
118022
Show that a group of order $180$ is not simple.
94141
$20$ people are sitting around a (circular) table. How many ways can we choose $3$ people, no two of whom are neighbors?
122558
Testing for players within a specified rectangular area
110347
Finding contiguous ranges in arrays
59419
Crafty solutions to the following limit
107171
Equilibrium of a tower of 2-d blocks
120822
A 10x10 table filled with 0 to 9 numbers
101642
Counting in a rectangular grid with obstacles
147901
Show that, in a group of n people, everyone has the same number of friends if..
140806
How do I tackle this combinatorics problem about married couples around a table?
136449
Combinatorics problem on $20$ people, $12$ months, and distinguishable groups
36510
Multidimensional array multiplication
66474
Cutting a rectangle into squares
118098
Rectangles Covering
2771
A group has odd number of elements iff each element is a square, $a=b^2$.