Question

Herons formula Find the area of an equilateral triangle whose perimeter is 60cm

Answer 1

Perimeter = 60cm 
1 side = 60/3 = 20 cm
√$s(s-a)(s-b)(s-c)$

s = 30 

√30(30-20)(30-20)(30-20)

=√30×10×10×10=√30000cm² = 100√3 cm²

Answer 2

perimeter = 60 cm
semi perimeter = 60 / 2 =- 30 cm
therefore length of each side ,a+a+a = 60 
3a = 60 
a = 20
Δ = √s (s-a)(s-b)(s-c)
= √30(30-20)(30-20)(30-20)
= √30*10*10*10
=√3*10*10*10*10
=10*10√3
=100√3 therefore the answer is 100√3cm².
          i hope it helps.......................^_^