Given:
a = 7 km
b = 6 km
c = 5 km
To find the Area of the triangle, we use Heron's formula, as follows:
[tex]A=\sqrt{s(s-a)(s-b)(s-c)}[/tex]
where s:
[tex]Semi\text{ }Perimeter\text{ }(s)=\frac{a+b+c}{2}=\frac{7+6+5}{2}=9km[/tex]
hence:
[tex]A=\sqrt{9\times(9-7)\times(9-6)\times(9-5)}=14.7km^2[/tex]
ANSWER
D. 14.7 km²
