A

polyomino of the

fifth order;

five connected squares.

The twelve pentominoes are:

X XX X X XX XX XXX XXX XX XX X XX
X X XX X XX X X X XX XX XXX X
X X X XX X XX X X X X X XX
X X X X
X

These twelve shapes are the

subject of many

tiling puzzles and other

recreational mathematics. The most well-known tiling problem involving these shapes is the tiling of a

rectangle using each pentomino once. Because their total

area is 60, several rectangles are possible: 3x20, 4x15, 5x12, 6x10.