Question

If the area of an equilateral triangle is $25\sqrt{3}c{m}^2$, then its perimeter = _____________________ cm.

• A. 10
• B. 30
• C. 45
• D. 60

Answer 1

The correct option is B

30

Area of an equilateral $△$ = $\frac{\sqrt{3}}{4}{a}^2$

$25\sqrt{3}=\frac{\sqrt{3}}{4}{a}^2$

$\therefore a^2=5^2\times 2^2$

$a=10cm$

Perimeter =$3a$

=$3\left(10\right)$

=$30cm$

Hence (B)