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Combinatorics Difficulty 1.0 Junior Find the answer Canada

In the diagram, how many of the $24$ circles are shaded?

IMG0

Figure for this problem

Pick one

Solution

In each row, exactly $3$ of the $6$ or one-half of the circles are shaded. Thus, one-half of the $24$ , that is, $12$ circles are shaded. Alternately, we could just count the $12$ shaded
circles.

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Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project.