11. The diagram shows a regular hexagon which has been divided into six regions by three of its diagonals. Two of these regions have been shaded. The total shaded area is $20 \mathrm{~cm}^{2}$.
What is the area of the hexagon?
A $40 \mathrm{~cm}^{2}$ B $48 \mathrm{~cm}^{2}$ C $52 \mathrm{~cm}^{2}$ D $54 \mathrm{~cm}^{2}$ E $60 \mathrm{~cm}^{2}$
11. B The diagram shows that the hexagon may be divided into twelve congruent triangles, of which five are shaded. Let the area of each of these triangles be $a \mathrm{~cm}^{2}$. Then $5 a=20$, so $a=4$. Hence the area of the hexagon, in $\mathrm{cm}^{2}$, is $12 a=12 \times 4=48$.