In the diagram, the $5 \times 6$ grid is made out of thirty $1 \times 1$ squares. What is the total length of the six solid line segments shown?
(A) 6
(B) 12
(C) 16
(D) 18
(E) 20

![](https://cdn.mathpix.com/cropped/2024_04_20_6ed09463f225f8ba1f07g-044.jpg?height=331&width=379&top_left_y=913&top_left_x=1342)
Since the grid is made up of $1 \times 1$ squares, then the lengths of the solid line segments, from top to bottom, are $5,1,4,2,3$, and 3 .

The sum of these lengths is $5+1+4+2+3+3=18$.

Alternatively, we could note that the first and second solid line segments can be combined to form a solid segment of length 6 . The same is true with the third and fourth segments, and with the fifth and sixth segments. Thus, the total length is $6 \times 3=18$.

ANSWER: (D)