Question

If the perimeter of an equilateral triangle is 90 m then find its area

Answer 1

$perimeter = s {}^{2} \\ s \times s = 90 \\ s = 30 \\ area = \ \sqrt{3 \:} \div 4 \times s {}^{2} \\ \sqrt{3 \: } \div 4 \times 30 \times 30 = 225 \sqrt{3}$