The side of an equilateral triangle is equal to the radius of a circle whose area is 154 cm2.

(b) $\frac{49 \sqrt{3}}{4} \mathrm{~cm}^{2}$

Area of a circle $=\pi r^{2}$

$\Rightarrow 154=\pi r^{2}$

$\Rightarrow r=\sqrt{\frac{154 \times 7}{22}}$

$=\sqrt{7 \times 7}$

$=7 \mathrm{~cm}$

The radius of the circle is equal to the side of the equilateral triangle.  

∴ r = a (Here, a is the side of the equilateral triangle.)

$a=7 \mathrm{~cm}$

$\therefore$ Area of the equilateral triangle $=\frac{\sqrt{3}}{4} a^{2}=\frac{\sqrt{3}}{4} \times 7 \times 7=\frac{49 \sqrt{3}}{4} \mathrm{~cm}^{2}$