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Printjmc
geometry junior
Problem
A "domino" is made up of two small squares:
Which of the "checkerboards" illustrated below CANNOT be covered exactly and completely by a whole number of non-overlapping dominoes? 
(A)
(B)
(C)
(D)
Solution
For a bunch of dominoes to completely tile a board, the board must have an even number of squares. The board clearly does not, so cannot be tiled completely.
Final answer
B