In the diagram, 30 identical small squares are shown.

How many of these 30 squares are shaded?
(A) 10
(B) 12
(C) 15
(D) 18
(E) 20

![](https://cdn.mathpix.com/cropped/2024_04_20_6ed09463f225f8ba1f07g-002.jpg?height=271&width=567&top_left_y=748&top_left_x=1126)
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 4 th with the 5 th.) Thus, again there are $\frac{1}{2} \times 30=15$ shaded squares.

ANSWER: (C)