The perimeter of an equilateral triangle is 60 cm, then the area is

Given,
perimeter = 60 cm
semi perimeter =

\frac{60}{2}

=30 cm.
So the length of each side will be,
a + a + a = 60
⇒3a = 60
⇒a =

\frac{60}{3}

⇒a = 20
∴ Area =

\sqrt{s (s - a) (s - b) (s - c)}

⇒ Area =

\sqrt{30 (30 - 20) (30 - 20) (30 - 20)}

\sqrt{30 \times 10 \times 10 \times 10}

\sqrt{3 \times 10 \times 10 \times 10 \times 10}

⇒ Area =10 ×

10 \sqrt{3}

⇒ Area = 100

\sqrt{3}

cm2 Hence, option 4, 100

\sqrt{3}

cm2 is correct.

JEE