9. In the figure, the perimeter of the equilateral triangle is equal to that of the regular hexagon. Given that the area of the equilateral triangle is $10 \mathrm{~cm}^{2}$, then the area of the regular hexagon is $\qquad$ $\mathrm{cm}^{2}$
【Answer】15
Analysis: Let the length of each side of the regular hexagon be $\mathrm{a}$, then the length of each side of the equilateral triangle is $2 \mathrm{a}$. After division, the area of each small triangle is the same, $10 \div 4 \times 6=15 \mathrm{~cm}^{2}$