22

Part of 2018 Iran MO (1st Round)

Problems(1)

1x2 tiles covering a 4x4 area - Iran First Round 2018, P22

Source:

There are eight congruent

1\times 2

tiles formed of one blue square and one red square. In how many ways can we cover a

4\times 4

area with these tiles so that each row and each column has two blue squares and two red squares?

combinatoricscountingtiles