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Mathematics-Online problems:
Problem of the week
The figure shows some arrays of a
-matrix of black and white pixels.
How many different arrays exist having
(a)
exactly one black pixel in each row and each column,
(b)
at least 4 black pixels,
(c)
exactly 4 black pixels joined together? (Each of the black pixels must have at least one side in common with another black pixel.)
Answer:
(a)
(b)
(c)
[
solution to the problem of the previous week
]