The correct option is B 4√15 cm2
Let each of its equal sides be x.
Then, 2x+4=20 ⇒x=8cm
Hence, the sides are 8 cm, 8 cm and 4 cm.
Using the Heron's formula,
Area(A)=√s(s−a)(s−b)(s−c)
where s = semi- perimeter and a,b,c are the three sides of the triangle.
Semi−Perimeter(s)=perimeter2
=202 =10 cm
A=√10 (10−8)(10−8)(10−4)
=√10×2×2×6
=4√15 cm2