The three sides of a triangle are 5m, 6m and 7m respectively. Which one below is the area of the triangle?

×
15 m^2

✓
6 \sqrt{6} m^2

×
21 m^2

×
9 m^2
The three sides of a triangle are 5m, 6m and 7m respectively. Which one below is the area of the triangle?
15 m^2
6 \sqrt{6} m^2
21 m^2
9 m^2
According to Helen's formula, the area of a triangle is
A = \sqrt{p(pa)(pb)(pc)} ,
in which a, b, c is the length of three sides of the triangle,
p = \dfrac{1}{2} (a+b+c)
\therefore A = \sqrt{9×4×3×2 } = 6 \sqrt{6}