In the diagram, 30 identical small squares are shown.
How many of these 30 squares are shaded?
, 2023
Pick one
Solution
From left to right, the number of shaded squares in each column
with shaded squares is 1, 3, 5, 4, 2.
Thus, the number of shaded squares is $1 + 3
+ 5 + 4 + 2 = 15$.
Alternatively, we could note that exactly one-half of the 30 squares are
shaded since each column with shaded squares can be paired with a column
of the same number of unshaded squares. (The 1st column is paired with
the 8th, the 2nd with the 7th, the 3rd with the 6th, and the 4th with
the 5th.) Thus, again there are 30 = 15$ shaded squares.
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