9. Three sectors of a circle are removed from a regular hexagon to form the shaded shape shown. Each sector has perimeter $18 \mathrm{~mm}$. What is the perimeter, in $\mathrm{mm}$, of the shaded shape formed?

A 48
B 50
C 52
D 54
E 56
9. D Let the length of the side of the hexagon be $x \mathrm{~mm}$ and the length of the arc of each sector be $l \mathrm{~mm}$. Then the radius of each sector is also $x \mathrm{~mm}$. Therefore $2 x+l=18$.
The perimeter, in $\mathrm{mm}$, of the shape formed when the three sectors are removed from the hexagon is $6 x+3 l=3(2 x+l)=3 \times 18=54$.