Skip to main content
OlympiadHQ

Browse · harp

Print

imc

counting and probability intermediate

Problem

The grid shown contains a collection of squares with sizes from to . How many of these squares contain the black center square?
problem
(A)
(B)
(C)
(D)
Solution
Since there are five types of squares: and We must find how many of each square contain the black shaded square in the center. If we list them, we get that There is of all squares, containing the black square There are of all squares, containing the black square There are of all squares, containing the black square There are of all squares, containing the black square * There is of all squares, containing the black square Thus, the answer is .
Final answer
D